Waste-treating agent

ABSTRACT

To treat waste containing harmful netals such as lead, cadmium, mercury, chromium, copper, nickel, zinc, etc., the waste is mixed with a treating agent containing, as the essential constituent component, solid acid(s) and/or cement and additionally a caking inhibitor, kneaded with water where necessary, then solidified by curing. Harmful metals are thereby stabilized in the thus-solidified cakes and are not released therefrom.

This application is a continuation of application Ser. No. 08/364,194filed Dec. 27, 1994, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a waste-treating agent, which iseffective for stabilizing waste containing harmful heavy metals, etc.,and to a method for treating waste using it.

2. Prior Art

Recently, about 48,000,000 tons/year (in 1988) of general waste andabout 310,000,000 tons/year (in 1985) of industrial waste were discardedin Japan. It is estimated that the former general waste will reach about80,000,000 tons/year and the latter industrial waste about 600,000,000tons/year in the year 2000. Of these, about 70% of general waste areincinerated while about 20% thereof are directly discarded. On the otherhand, about 40% of the industrial waste is recycled and about 30% isincinerated to reduce the volume and is then discarded, while about 30%is directly discarded in final garbage pits. Since the general waste andindustrial waste incinerated contain large amounts of harmful heavymetals, the legal controls on the treatment of these are beingreinforced noticeably.

As for garbage pits in urban areas, for example, color printed paper orcellophane in waste discarded into these pits contain cadmium (Cd), lead(Pb), chromium (Cr), mercury (Hg), arsenic (As), copper (Cu), etc.,while plastics discarded thereinto contain cadmium, lead, zinc (Zn),chromium, mercury, arsenic, etc. Incineration of such waste yields theashes of concentrated heavy metals. In many waste incineration systems,recently, the ashes are fractionated into main ash- comprising cindersfrom waste and fly ash that is collected in bag filters or the like andthe thus-fractionated ashes are collected separately. Both main ash andfly ash contain heavy metals, but fly ash easily releases heavy metalswhen it is discarded as it is. This occurs for the following reasons:Slaked lime or quick lime is introduced with air into the exhaust ductsin incineration systems so as to trap the hydrogen chloride gasgenerated by the incineration of the waste therein. The slaked lime orquick lime is bonded to the hydrogen chloride gas generated to formcalcium chloride, by which the hydrogen chloride gas concentration inthe exhaust gas from the incineration system is lowered. However, sincethe non-reacted slaked lime or quick lime remains present in the flyash, the fly ash becomes highly alkaline and has a pH of 12 or higher.However, since fly ash contains a high concentration of lead and sincethe lead is converted into lead hydrochloride under highly alkalineconditions to be soluble in water, the fly ash releases lead when it isdiscarded without being first processed. In order to prevent fly ashfrom releasing harmful heavy metals, such as lead, in such incinerationsystems, the fly ash is mixed with cement, water is added thereto andkneaded, the resulting mix is cured and solidified, and the resultingcake is discarded or is mixed with main ash and is used for landreclamation. However, cement is alkaline. Therefore, if a large amountof such cement is added to fly ash, the release of lead from the fly ashcannot be prevented. Thus, the conventional treatment method of merelysolidifying the fly ash with cement involves various problems, and ifthe use of the method is not limited, the method will cause secondaryenvironmental pollution.

Chelating agents have been used experimentally for the treatment of flyash. To fly ash which is highly alkaline and which has a high leadcontent, however, such a chelating agent must be added in an amount of6% by weight or more of the weight of the fly ash. If not, the amount ofthe metal to be released from the fly ash cannot be controlled to bewithin the regulated value or lower. In general, such chelating agentsare highly priced, namely their unit prices are from 50 times to 80times the unit price of cement. Therefore, it is considered that the useof such high-priced chelating agents results in the increase in theoperational costs.

Thus, it has become known that the stabilization of heavy metals in flyash is often difficult by the mere addition of cement or chelatingagents thereto. Various companies have produced kneading devices forkneading fly ash and a treating agent therefor, which are used inincineration systems. Such kneading devices have various kneadingcapacities. Even for kneading devices of the same type, sufficientkneading cannot be attained in some of them if the position throughwhich the kneaded mix is extruded out is not appropriate. In such cases,the effect of the treating agent for stabilizing harmful metals is notconstant.

As mentioned above, the current treating agents and the methods of usingthem have various problems. In addition, there is another problem inthat, here in Japan the amount of the land which is reclaimable withwaste is small. Given this situations, it is desirable to have awaste-treating agent, by which harmful heavy metals in waste arestrongly stabilized so that the thus-stabilized metals are not released,even when a small amount of such a waste-treating agent is added to thewaste, and also to provide a method for effectively treating waste.

The object of the present invention is to provide such a waste-treatingagent effective for stabilizing waste containing harmful heavy metals,etc. and also a method for treating waste with the agent. In particular,the object of the present invention is to provide a waste-treatingagent, by which harmful heavy metals contained in alkaline fly ash to bedischarged from garbage incineration systems, such as those mentionedabove, are stabilized in such a way that the thus-stabilized metals arenot released out, and also to provide a method for effectively treatingwaste with the agent.

SUMMARY OF THE INVENTION

We, the present inventors have assiduously studied so as to solve theabove-mentioned problems and, as a result, have found a waste-treatingagent by which the object of the present invention can be attained.Specifically, the treating agent of the present invention is awaste-treating agent consisting, as the essential constitutivecomponent, at least one or more solid acids. In addition, we, thepresent inventors have further found that the treating agent preferablycontains, as the said solid acid component, at least one of aluminiumsilicates and silicon dioxide having a high specific surface area.

The solid acids to be employed in the present invention will bedescribed in more detail hereinunder. Various kinds of solid acids canbe employed in the present invention. First mentioned are natural clayminerals, such as acid clay, Fuller's earth, montmorillonite, bentonite,kaolin, clarite, Floridine (name of a product produced by FloridineCompany), etc., that have been Processed to have a specific surface areaof from 150 m² /g to 500 m² /g.

When dried, the acid clay forms porous granules having a large internalsurface area. When treated with sulfuric acid, the acid clay partlyreleases acid-soluble components such as aluminium, etc. As a result,the specific surface area and the pore volume of the thus-treated acidclay are increased. The thus-treated acid clay is referred to asactivated clay. As the derivative from the acid clay to be obtained byfurther treating it with sulfuric acid thereby removing aluminatherefrom, known is silicon dioxide. As solid acids which are similar tothe acid clay, known are Fuller's earth and Florida earth.

It is preferred that the above-mentioned acid clay and other clayminerals which are used in the present invention are processed so as tohave an enlarged specific surface area.

As the solid acids for use in the present invention, also mentioned aresolidified acids that are produced by adhering sulfuric acid, phosphoricacid, malonic acid or the like to silica gel or alumina or by adheringphosphoric acid under heat to diatomaceous earth, silica gel, quartzsand or titanium oxide. The important properties of these silica gel,aluminium and others, which are carriers, include high porosity, a largesurface area, a large bulk density and high mechanical strength. Itcannot be said unconditionally which one or more of these propertieshave a close relation to the property which stabilizes harmful metals,as depending on the harmful metals to be stabilized with the agent andon the physical properties of the waste to be treated therewith. Ingeneral, however, those having a larger surface area are better.Therefore, those having a specific surface area of 150 m² /g or more arepreferred. In order to make the carrier carry the acid under heat, theheating may be conducted at 200° C. to 1000° C.

As the solid acids for use in the present invention, further mentionedare polyanionic compounds and cation-exchange resins. Polyanioniccompounds have plural anionic functional groups in one molecule. Suchpolyanionic compounds are preferably employed in the present invention,as they can remove large amounts of heavy metals from waste. Thepolyanionic compounds may have the same or different anionic functionalgroups in one molecule. As specific examples of such polyanioniccompounds, mentioned are polyacrylic acid, polyvinylsulfonic acid,polystyrenesulfonic acid, polystyrenephosphoric acid, polyphosphoricacid, etc. Cation-exchange resins have anionic functional groups fixedon a water-insoluble porous carrier. As the carrier, mentioned areinorganic substances such as glass, silica, alumina, etc., as well aspolymers of styrene, alkylbenzenesulfonic acids, etc. Anionic functionalgroups are bonded to these carriers. As the anionic groups, mentionedare monoanions such as thiol group, sulfonato group, sulfato group,carboxyl group, etc., and polyanions.

As the solid acids for use in the present invention, still furthermentioned are ZnO, Al₂ O₃ and their heat-treated products, TiO₂ and itsheat-treated product, CeO₂ and its heat-treated -product, As₂ O₃, V₂ O₅,SiO₂ and their heat-treated products, and Sb₂ O₅. These oxides arepreferred, since their structures are stable and large amounts of theirproducts having desired properties can be obtained by processing naturalsubstances.

As still other examples of the solid acids for use in the presentinvention, mentioned are the following:

COSO₄, MnSO4 and their heat-treated products;

NiSO₄ and its heat-treated product;

CuSO₄ and its heat-treated product;

CoSO₄, CdSO₄ and their heat-treated products;

SrSO₄, ZnSO₄ and their heat-treated products;

MgSO₄, FeSO₄ and their heat-treated products;

Heat-treated BaSO₄, KHSO₄, K₂ SO₄, (NH₄)₂ SO₄, Al₂ (SO₄)₃, Fe₂ (SO₄)₃,Cr₂ (SO₄)₃, Ca(NO₃)₂.4H₂ O, Bi(NO₃)₃.5H₂ O, Zn(NO₃)₂.6H₂ O, Fe(NO₃)₂.9H₂O, CaCO₃, Zr phosphate, Ti phosphate, and aluminium phosphates such asAl(H₂ PO₄)₃, Al₂ (HPO₄)₃, AlPO₄, etc.;

PbCl₂, HgCl₂ and their heat-treated products;

CuCl₂ and its heat-treated product;

AlCl₃ and its heat-treated product;

SnCl₂ and its heat-treated product;

CaCl₂, AgCl₂, H₂ WO₄, AgClO₄, Mg(ClO₄)₂, ZnS and their heat-treatedproducts;

CaS;

Aluminium silicates; etc.

Where the solid acids to be used in the present invention are selectedfrom those above-mentioned, those which are as low-priced as possibleare preferred in view of the subject matter of the present invention. Inaddition, the following points shall be taken into consideration.

(1) In compounds containing any of Pb, As, Hg, Cd, etc., these metalsthemselves correspond to harmful metals which shall be controlled withrespect to their amounts to be released from the compounds. Therefore,before their use, these compounds shall be subjected to a released metalcontent test, by which their safety shall be confirmed.

(2) The optimum solid acids differ, depending on the waste to be treatedwith them. Therefore, before their use, the solid acids shall be testedby a released metal content test, by which their effect shall beconfirmed.

In view of these, preferred embodiments of the solid acids for use inthe present invention are aluminium sulfate, aluminium silicates,silicon dioxide, etc.

Regarding the shape of the above-mentioned solid acids for use in thepresent invention, the acids are preferably in the forms of powders inview of their reactivity. The combined use of a plurality of the solidacids, according to the object of the present invention, is within thescope of the invention.

Aluminium silicates which are used in the present invention aredescribed in detail hereinunder.

Aluminium silicates are those to be derived from silicon dioxide bysubstituting a part of the silicon in the dioxide with aluminium,including, for example, natural aluminium silicates such as pumice, flyash, kaolin, talc, bentonite, activated clay, diatomaceous earth,zeolite, etc., and synthetic aluminium silicates.

The aluminium silicates for use in the present invention are powders.Where a solid substance is made into a powder, the resulting powder isto have physicochemically particular properties. The reasons for thisare considered to be mostly as a result of the effect of the surfaces ofthe particles constituting the powder. In order to examine the surfaceproperties of the powder, it is recommended that the sum of the surfaceareas of all the particles to be in the unit amount of the powder, thatis, the specific surface area of the powder be determined, rather thanthat the size of each particle in the powder or the distribution of theparticles in the same is determined. To determine such a specificsurface area of a powder, there are known vapor adsorption methods (BETmethod, Harkins-Jura's relative method), liquid-phase adsorptionmethods, heat immersion methods (Harkins-Jura's absolute method) andpermeation methods (Blaine method), such as those described in theliterature (Illustration of Physical Properties of Powdery Substances,edited by the Powder Engineering Society of the Nippon Powder IndustrialAssociation, 1975). These methods depend on the different principles ofmeasurement and the results to be obtained by them are not always thesame. The specific surface area as referred to herein indicates a valueobtained by a BET surface area method. Table 1 below shows reportedvalues of specific surface areas of various powders.

                  TABLE 1                                                         ______________________________________                                                     Specific Surface                                                                             Method for                                        Name of Powder                                                                             Area (m.sup.2 /g)                                                                            Measurement                                       ______________________________________                                        Activated Clay                                                                             200-300        BET Method (N.sub.2)                              Kaolin Clay  15-30          BET Method (N.sub.2)                              Flux-calcined                                                                              1-3            BET Method (N.sub.2)                              Diatomaceous Earth                                                            Diatomaceous Earth                                                                         12-40          BET Method (N.sub.2)                              Fly Ash      0.25-0.36      Blaine Method                                     Agalmatolite 9.6            BET Method (N.sub.2)                              Portland Cement                                                                            0.28-0.55      Blaine Method                                     ______________________________________                                         (Reprinted from Illustration of Physical Properties of Powdery Substances     edited by the Powder Engineering Society of the Nippon Powder Industrial      Association, 1975)                                                       

It is desirable that the aluminium silicates for use in the presentinvention have a large specific surface area. This is because thecapacity of the waste-treating agent of the present invention forstabilizing harmful metals increases with the increase in the specificsurface area of the aluminium silicate to be contained in the agent.However, aluminium silicates having a too large specific surface areaare unfavorable. This is because, if the aluminium silicate in thewaste-treating agent has a too large specific surface area, the bulkdensity of the agent is lowered so that the handling of the agent inmixing it with waste becomes difficult, although the agent may stabilizeharmful metals without releasing them. For these reasons, it isdesirable that the aluminium silicates for use in the present inventionhave a specific surface area of from 150 m² /g to less than 1000 m² /g,more preferably from 200 m² /g to less than 700 m² /g.

The aluminium atoms in aluminium silicates are four-coordinate andsix-coordinate ones. It is desirable that the aluminium atoms in thealuminium silicates for use in the present invention are four-coordinateones. Aluminium silicates having four-coordinate aluminium atoms shallcarry other cations in the lattices, since the three-valent cation ofaluminium atom in these compounds cannot maintain by itself theelectrically neutral property of the compounds. Therefore, the amountsof heavy metals to be stabilized by such aluminium silicates havingfour-coordinate aluminium atoms are large. As opposed to these,aluminium silicates having six-coordinate aluminium atoms cannotadditionally take other cations thereinto since the six-coordinatealuminium atom is electrically neutral. Therefore, it is preferred thatthe aluminium silicates for use in the present invention havefour-coordinate aluminium atoms in an amount of 50% or more, morepreferably 70% or more, of total aluminium atoms therein. To measure thecoordination number of aluminium atoms, NMR is preferably employed. Forinstance, when ²⁷ Al-NMR for an aluminium silicate sample is measured,using AlCl₃.6H₂ O as the reference substance, the peak of the chemicalshift of six-coordinate aluminium atom appears in the vicinity of 0 ppm,while that of four-coordinate aluminium atom in the vicinity of 55 ppm.From the proportions of these peak areas appearing in these positions,the ratio of the six-coordinate aluminium atoms to the four-coordinatealuminium atoms, all existing in the aluminium silicate sample measured,can be known.

Various crystalline, amorphous, non-crystalline and vitreous aluminiumsilicates are known. Of these, any and every powdery aluminium silicatecan be used in the present invention. Dried or calcined aluminiumsilicates can also be used in the present invention. However, formolecular sieving, zeolite cannot be used instead of the aluminiumsilicate in the present invention. Almost all of the specific surfaceareas of such zeolite are distributed in fine pores having a porediameter of 1 nm or less so that only molecules smaller than these finepores limitatively adsorb to the zeolite. However, since solventmolecules adsorb to such fine pores of the zeolite in a solution, whilea minor amount of water thereto even in air, strongly and denselywithout leaving any void space between the molecules adsorbed.Therefore, heavy metal ions such as lead ions, etc., that have beenreleased from waste, cannot adsorb to the zeolite with the result that,even though it has a large specific surface area, the zeolite does nothave a sufficient capacity for stabilizing heavy metals. In addition,different heavy metal ions have significantly different ionic radii,depending on the kind of the ions, and they are coordinated with manyimpurity ions existing in waste to form complex ions having enlargedionic radii. Therefore, aluminium silicates having a narrow pore sizedistribution, such as zeolite, are not preferred for use in the presentinvention while those having a broad pore size distribution or havingpores with broadly varying surface areas are desirably used in thepresent invention. The aluminium silicates for use in the presentinvention are not so-called pozzolan substances such as fly ash shown inTable 1 above and incineration furnace ash, and these do not includeactivated clay having a small specific surface area, kaolin clay,diatomaceous earth, agalmatolite, etc. When the waste-treating agent ofthe present invention is previously prepared and stored before use, itis preferred that the agent is anhydrous or that it is substantiallyfree from water in order that the deterioration of the -cement and ofthe other additives therein due to absorption of water is notaccelerated during storage. Any of the synthetic aluminium silicates andnatural aluminium silicates satisfying these requirements can beemployed in the present invention. As one example of the syntheticaluminium silicates, mentioned is a synthetic aluminium silicate to beobtained by adding a soluble aluminium salt to a solution of sodiumsilicate. As one example of the natural aluminium silicates, mentionedis a fine powdery aluminium silicate to be obtained by treating acidclay with an acid followed by powdering it. However, these aluminiumsilicates are not to be limitative when used in the present invention.

Next, silicon dioxide for use in the present invention will be describedin detail hereinunder. It is desirable that silicon dioxide for use inthe present invention is a powder having a large specific surface areasince it has an excellent effect of stabilizing heavy metals. This isbecause the capacity of the waste-treating agent of the presentinvention for stabilizing harmful metals increases with the increase inthe specific surface area of the silicon dioxide to be contained in theagent. However, silicon dioxide having a too large specific surface areais unfavorable. This is because, if the silicon dioxide in thewaste-treating agent has a too large specific surface area, the bulkdensity of the agent is lowered so that the handling of the agent inmixing it with waste becomes difficult, although the agent may stabilizeharmful metals without releasing them. For these reasons, it isdesirable that the silicon dioxide for use in the present invention hasa specific surface area of from 150 m² /g to less than 1000 m² /g, morepreferably from 200 m² /g to less than 700 m² /g.

Silicon dioxide has various structures composed oftetrahedral-structured SiO₄ units. Therefore, the degree of degeneracy Q(Q=1 to 4), which means the number of oxygen atoms in the SiO₄tetrahedron unit that are bonded to the adjacent silicon atom bycovalent bond is referred to so as to describe the state of the siliconatom in silicon dioxide. When the silicon atom in a certain silicondioxide has a Q of 4, all the bonds to the silicon atom therein arestrong Si--O--Si bonds so that this atom is difficult to bond to heavymetal ions such as lead ions. As opposed to this, silicon atom having aQ of 1, 2 or 3 has a Si--O bond or Si--O--X bond in which X represents ahydrogen atom or a metal atom such as Na, Ca or the like. In this case,heavy metal ions such as lead ions are bonded to the Si--O bond or arereplaced for the X atom and thus are stabilized. Therefore, silicondioxide in which silicon atoms with Q4 are as few as possible ispreferred for use in the present invention. Precisely, it is preferredthat silicon dioxide for use in the present invention has silicon atomswith Q4 in an amount of 85% or less, more preferably 80% or less of allof the silicon atoms therein. To determine the amount of silicon atomswith Q4 in silicon dioxide, NMR is preferably employed. For instance,when ²⁹ Si--NMR for a silicon dioxide sample is measured, using (CH₃)₃Si(CH₂)₃ SO₃ Na as the reference substance, the peak of the chemicalshift of silicon atom with Q4 appears in the vicinity of -113 ppm, whilethat of silicon atom with Q3 in the vicinity of -104 ppm and that ofsilicon atom with Q2 in the vicinity of -95 ppm. From the proportions ofthese peak areas appearing in these positions, the proportion of thesilicon atoms with Q4 existing in the silicon dioxide sample measuredcan be determined.

Various crystalline, amorphous, non-crystalline and vitreous silicondioxides are known. Of these, any and every powdery silicon dioxide canbe used in the present invention. When the waste-treating agent of thepresent invention is previously prepared and stored before use, it ispreferred that the agent is anhydrous or that it is substantially freefrom water in order that the deterioration of the cement and of theother additives therein due to absorption of water is not acceleratedduring storage. Any of synthetic silicon dioxide products and naturalsilicon dioxide substances satisfying these requirements can be employedin the present invention. The synthetic silicon dioxide products can beproduced from sodium silicate and acids. Depending on the reactionconditions such as the reaction temperatures and the concentrations ofthe starting materials used and also on the other conditions for dryingand powdering the products formed, various silicon dioxide productshaving various physical properties are produced. As examples of thenatural silicon dioxide substances, mentioned are fine powdery silicondioxides to be obtained by treating acid clay or activated clay with anacid followed by powdering it. However, these silicon dioxides are notto be limitative when used in the present invention.

The surface potential of the above-mentioned aluminium silicates andsilicon dioxides for use in the present invention has a great influenceon the amounts of ions to be adsorbed onto these powdery substances. Itis preferable that the aluminium silicates and the silicon dioxides foruse in the present invention have a negative surface potential. Thesepowdery substances having a negative surface potential have manynegatively-charged adsorption sites on the surfaces of the particles, towhich harmful metal cations are adsorbed and stabilized thereon.Therefore, it is desirable that the surface potential of the aluminiumsilicates and the silicon dioxides for use in the present invention is-15 mV or lower within a pH range of 7 or more. To measure the surfacepotential of these powdery substances, known are a streaming potentialmethod and an electrophoresis method. Since the powdery aluminiumsilicates and silicon dioxides for use in the present invention aredifficult to suspend in aqueous solutions, as they have large particlesizes, it is recommended their surface potentials be measured by astreaming potential method. In the present invention, a 5% KCl solution,to which NaOH or HCl had been added thereby adjusting its pH to between2 and 12, was used as the solution for the measurement of the surfacepotentials of the powdery substances.

The waste-treating agent of the present invention may contain, inaddition to the above-mentioned solid acid(s), cement as the essentialconstitutive component. The cement for use in the present inventionincludes, for example, hydraulic cement such as portland cement (normalportland cement, ultra-high-early-strength portland cement, moderateheat portland cement, sulfate-resistant portland cement, etc.), mixedcement (fly ash, slag cement, silica, etc.), etc., and air-settingcement such as lime, gypsum, etc. In addition, lime-mixed cement canalso be used. Two or more of these can be mixed for use in the presentinvention. The cement for use in the present invention is notspecifically limited, and any appropriate cement that shall be selectedin accordance with the properties of the waste to be treated with thetreating agent of the present invention and the conditions for treatingthem can be employed in the present invention.

The waste-treating agent of the present invention may further contain,in addition to the above-mentioned essential constitutive components ofsolid acids and cement, auxiliary components such as reducing agents,allophane, bentonite, etc. In addition, this may also contain awater-proofing agent (calcium chloride, polymer emulsions, water-solublepolymers, higher fatty acids, etc.), a coagulation accelerator, asolidification accelerator, etc. As the reducing agents, usable aresodium thiosulfate, thiourea, ferrous chloride, ferrous sulfate, sodiumsulfite, hydrosulfite, etc. Of these, more preferred are sodiumthiosulfate and thiourea. Where the above-mentioned auxiliary componentsare added to the waste-treating agent of the present invention, it isconsidered that the treating agent can be, after having been mixed withwaste containing harmful heavy metals, kept in a reductive condition dueto the reducing agent contained therein, before the cement in the agentis solidified. It is considered that allophane and bentonite willpromote the formation of ettringite in cement in the waste-treatingagent. In addition, allophane and bentonite will have an physicallyadsorbing effect. Further, zeolite and active charcoal may be added tothe waste-treating agent of the present invention so as to augment theeffect of the agent. Therefore, when the compounds selected from theabove-mentioned groups are added to the waste-treating agent of thepresent invention comprising cement and solid acid(s) as the essentialconstitutive components or to aluminium silicates or silicon dioxideshaving a large specific area, as auxiliary components, it is expectedthat the resulting mixtures can stabilize heavy metals more effectively.

The mixing ratio of cement to solid acid(s) in preparing thewaste-treating agent of the present invention will be describedhereinunder. The mixing ratio of cement to solid acid(s) may be suitablydetermined. In general, the content of solid acid(s) in thewaste-treating agent is from 10 to 80% by weight, preferably from 20 to60% by weight. If the content is less than the range, the stabilizationof harmful metals by the waste-treating agent is not satisfactory. Thelarger the content of solid acid(s), the more the harmful heavy metalsstabilized, while the thus-stabilized metals are not released. However,to satisfactorily stabilize harmful heavy metals, the content of solidacid(s) within the above-mentioned range is sufficient. If the contentof solid acid(s) is larger than the defined range, this excess of solidacid(s) rather retards the solidification of cement in thewaste-treating agent so that much time is needed for the solidificationof the agent. In addition, the excess of solid acid(s) will unfavorablylimit the addition of other components to the waste-treating agent.Moreover, since solid acids having a large specific area are apt to bebulky, the mixing of an excessive amount of solid acid(s) and cementwill be difficult and insufficient so that it becomes impossible toproduce a large amount of a uniform waste-treating agent. For thesereasons, the addition of an excessive amount of solid acid(s) to thewaste-treating agent of the present invention is unfavorable.

The mixing ratio of cement to aluminium silicate and silicon dioxide inpreparing the waste-treating agent of the present invention may besuitably determined. In general, the content of aluminium silicate andsilicon dioxide in the waste-treating agent is from 10 to 80% by weight,preferably from 20 to 60% by weight. As mentioned hereinabove, however,since the effect of aluminium silicate and silicon dioxide having a highspecific surface area for stabilizing heavy metals includes not onlytheir intrinsic effect as solid acids but also their effect of makingheavy metal ions adsorbed thereto. Therefore, the effect of aluminiumsilicate and silicon dioxide of stabilizing heavy metals varies,depending on the surface area of the aluminium silicate and silicondioxide relative to the unit amount of the waste-treating agentscontaining them. Accordingly, it is recommended that the amounts ofaluminium silicate and silicon dioxide to be added to cement aredetermined on the basis of the surface area of the aluminium silicateand silicon dioxide per the unit amount of the waste-treating agentcontaining them. Precisely, it is preferred that the surface area of thealuminium silicate and silicon dioxide to be contained in 1 g of thewaste-treating agent of the present invention is 50 m² /g or more, morepreferably 100 m² /g or more.

Next, methods for preparing the waste-treating agent of the presentinvention will be described hereinunder. To prepare the waste-treatingagent, for example, cement, aluminium silicate, silicon dioxide, solidacid(s), etc. may be mixed anytime before use or may be mixed justbefore use. If desired, cement, solid acid(s) and other components areadded to the waste to be treated therewith all at a time, and these aremixed so as to treat the waste along with them. In the former method ofpreviously mixing the components of the waste-treating agent, the meansof how to mix them and the order of their addition are not specificallydefined. Where the waste-treating agent prepared by previously mixingthe constitutive components is stored, it is recommended that the agentcontain water as little as possible, as in ordinary cement. If thewaste-treating agent is stored in a closed condition, it is stable likeordinary cement. Aluminium silicate and silicon dioxide can be employedsingly or in a combination of the two. In addition, aluminium silicateand/or silicon dioxide can be mixed with cement and other solid acid(s).Needless-to-say, a combination of aluminium silicate and silicon dioxidecan be mixed with cement, etc. The waste-treating agent of the presentinvention, if containing cement, can be solidified to a cake having anelevated mechanical strength. The thus-shaped object can be re-used. Theagent containing cement additionally exhibits the intrinsic heavymetal-stabilizing ability of cement. In addition, since cement isalkaline, the waste-treating agent containing cement and solid acid(s)can control the pH value of the waste treated with the agent.

Next, methods of treating waste with the treating agent of the presentinvention will be described hereinunder. To treat waste with thewaste-treating agent of the present invention, the agent is added to thewaste, then water is optionally added thereto, and these are kneaded,cured and solidified. As one preferred embodiment of the presentinvention, waste such as dust or fly ash are collected in a hopper, towhich added is the waste-treating agent of the present invention whichis in a separate hopper. These are mixed optionally along with wateradded thereto, then sufficiently kneaded and extruded out into a shapingdevice. According to the conventional method for treating waste onlywith cement, in general, from 10 to 30 parts by weight of cement areadded to 100 parts by weight of trash or waste and these are kneaded.According to the method of using the waste-treating agent of the presentinvention, however, much better results can be obtained if the agentcontains the same amount of cement as that in the conventional method.Therefore, if one desires to attain the same heavy metal-stabilizingeffect by using the waste-treating agent of the present invention asthat attainable by the use of cement only, the amount of the agent ofthe present invention to be added to the waste may be smaller than thatof the cement only to be added thereto. Thus, using the waste-treatingagent of the present invention, the volume of the solidified matters tobe formed after treatment of the waste with the agent can be reduced. Toheavy metals which are insufficiently stabilized by the conventionalmethod of using cement only, the same amount of the waste-treating agentof the present invention as that of cement to be used in theconventional method shall be added, by which such heavy metals aresufficiently stabilized.

As already mentioned hereinabove, it is generally known that Pb in flyash resulting from incineration of waste is often released out therefromunder alkaline conditions. Slaked lime is introduced along with air intoincineration furnaces in order to reduce the amount of hydrogen chloridegas to be generated during incineration of garbage collected in urbanareas. Therefore, fly ash collected in electric dust collectors and flyash collected in bag filters under such operational conditions releasean especially large amount of Pb. Since the waste-treating agent of thepresent invention contains solid acid(s), such alkaline waste may bemade nearly neutral by adding the agent thereto, due to the effect ofthe solid acid(s) in the agent. The waste-treating agent of the presentinvention has been developed on the basis of this technical concept.However, the addition of the agent of the present invention to alkalinewaste does not always result in the lowering of the pH value of thewaste, although the expected effect of the agent for inhibiting therelease of Pb from the waste to which the agent was added has beenconfirmed. Therefore, the effect and the mechanism of the solid acid(s)in the waste-treating agent of the present invention are not completelyclear at present.

The mechanism of aluminium silicate and silicon dioxide having a largespecific surface area, which are used in the present invention, forstabilizing harmful heavy metals may be presumed to essentially comprisean effect of chemically and physically adsorbing harmful metal ions andan effect of coagulating colloidal particles containing harmful metalsfollowed by adsorbing the thus-coagulated particles. Aluminium silicateand silicon dioxide having a large specific surface area act also assolid acids.

Where industrial waste containing harmful heavy metals as well as EP ashand bag ash (especially, EP ash and bag ash into which slaked lime orquick lime has been introduced along with air) to be discharged fromincineration furnaces where garbage collected in urban areas areincinerated are treated with the waste-treating agent of the presentinvention, harmful heavy metals, especially Pb, are efficientlystabilized, while the amount of the these metals that are released fromthe treated waste is reduced. Thus, the waste-treating agent of thepresent invention is extremely effective for stabilizing harmful heavymetals in waste. In addition to Pb, other harmful heavy metals such ascadmium, mercury, chromium, copper, nickel, zinc, etc. can be stabilizedby the treating agent of the present invention. Further, thewaste-treating agent of the present invention can be used forstabilizing slurry sludge and dewatered cake sludge that are dischargedfrom semiconductor plants or metal-plating plants after treatment ofvarious waste liquids from such plants, harmful dust collected fromelectric smelting furnaces and other apparatuses at steel manufacturingplants so as to protect the working environment of these plants, fly ashfrom incineration furnaces for incinerating city garbage, and harmfulheavy metals to be contained in soil contaminated due to the disposal ofwaste for land reclamation, and the thus-stabilized harmful heavy metalsare prevented from being released.

DETAILED DESCRIPTION OF EXAMPLES

Next, the present invention will be described in more detail withreference to the following examples, which, however, are not intended torestrict the scope of the present invention. Prior to referring to theexamples, the physical properties of various aluminium silicates andsilicon dioxides used in the following examples and comparative examplesare shown in Tables 2 and 3 below.

                  TABLE 2                                                         ______________________________________                                        Physical Properties of Various Aluminium Silicate                                     Specific                 Four-                                                Surface  Al.sub.2 O.sub.3                                                                       SiO.sub.2                                                                            Coordinate                                   Aluminium                                                                             Area     Content  Content                                                                              Al Atom pH of                                Silicate                                                                               m.sup.2 /g!                                                                            %!       %!     %!     Liquid                               ______________________________________                                        Aluminium                                                                             500      10.9     64.1   79.8    6.8                                  Silicate (1)                                                                  Aluminium                                                                             250      10.5     64.5   84.0    6.8                                  Silicate (2)                                                                  Aluminium                                                                             600      --       --     77.6    --                                   Silicate (3)                                                                  Aluminium                                                                             280      11.2     68.0   79.0    7.5                                  Silicate (4)                                                                  Aluminium                                                                             250      10.3     61.4   --      6.6                                  Silicate (5)                                                                  Aluminium                                                                             250      10.6     62.3   --      6.7                                  Silicate (6)                                                                  Aluminium                                                                             100       9.5     82.0   --      10.4                                 Silicate (7)                                                                  Aluminium                                                                             110      26.0     66.0   --      7.0                                  Silicate (8)                                                                  Aluminium                                                                             250       9.8     79.2   37.0    --                                   Silicate (9)                                                                  ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                        Physical Properties of Various Silicon Dioxides                                       Specific                                                                      Surface                   Mean                                        Silicon Area     SiO.sub.2        Particle                                                                             pH of                                Dioxide (m.sup.2 /g)                                                                           Content (%)                                                                             Q4 (%) Size (μm)                                                                         Liquid                               ______________________________________                                        Silicon 429      93.7      75.2   5.1    7.4                                  Dioxide (1)                                                                   Silicon 165      94.9      --     5.5    6.5                                  Dioxide (2)                                                                   Silicon 193      95.2      --     6.8    5.8                                  Dioxide (3)                                                                   Silicon 240      93.85     74.1   5.3    5.0                                  Dioxide (4)                                                                   Silicon 120      93.05     86.7   5.0    5.0                                  Dioxide (5)                                                                   Silicon 109      90.9      --     7.5    10.6                                 Dioxide (6)                                                                   ______________________________________                                    

The surface potentials of the above-mentioned aluminium silicate (1),aluminium silicate (9) and silicon dioxide (1) at varying pH values areshown in Table 4, Table 5 and Table 6 below, respectively.

                                      TABLE 4                                     __________________________________________________________________________    Surface Potentials of Aluminium Silicate (1)                                  __________________________________________________________________________    pH   2.4                                                                              3.2                                                                              4.7                                                                              6.4                                                                              7.0                                                                              9.2                                                                              9.8                                                                              10.7                                                                              11.5                                                                             12.4                                         Surface                                                                            -6 -10                                                                              -13                                                                              -14                                                                              -14                                                                              -16                                                                              -16                                                                              -18 -18                                                                              -21                                          Potential                                                                     (mV)                                                                          __________________________________________________________________________

                                      TABLE 5                                     __________________________________________________________________________    Surface Potentials of Aluminium Silicate (9)                                  __________________________________________________________________________    pH   2.1                                                                              3.1                                                                              4.5                                                                              5.8                                                                              6.8                                                                              7.6                                                                              8.7                                                                              9.2                                                                              10.0                                                                             11.3                                                                             12.2                                       Surface                                                                            -5 -6 -9 -9 -10                                                                              -10                                                                              -9 -8 -7.6                                                                             -12                                                                              -14                                        Potential                                                                     (mV)                                                                          __________________________________________________________________________

                                      TABLE 6                                     __________________________________________________________________________    Surface Potential of Silicon Dioxide (1)                                      __________________________________________________________________________    pH   2.3                                                                              3.3                                                                              4.9                                                                              6.3                                                                              7.3                                                                              8.8                                                                              9.3                                                                              9.9                                                                              10.6                                                                             11.6                                                                             12.2                                       Surface                                                                            -9 -13                                                                              -14                                                                              -20                                                                              -20                                                                              -19                                                                              -20                                                                              -20                                                                              -21                                                                              -22                                                                              -29                                        Potential                                                                     (mV)                                                                          __________________________________________________________________________

EXAMPLE 1

70 parts by weight of ordinary portland cement (produced by Ube CementCo.) were mixed with 30 parts by weight of activated clay (produced byMizusawa Chemical Industry Co.) having a specific surface area of 150 m²/g, 180 m² /g, 190 m² /g, 220 m² /g or 250 m² /g measured by a BETmethod, as a solid acid, to prepare a waste-treating agent of thepresent invention. As a comparative agent, used was ordinary portlandcement. The compositions of the treating agents thus prepared are shownin Table 7 below.

                  TABLE 7                                                         ______________________________________                                        Compositions of Treating Agents                                                                     Activated                                                                              Specific                                                 Cement      Clay     Surface Area                                             (parts by   (parts by                                                                              of Activated                                   Type      weight)     weight)  Clay (m.sup.2 /g)                              ______________________________________                                        Treating  70          30       150                                            Agent 1-1                                                                     Treating  70          30       180                                            Agent 1-2                                                                     Treating  70          30       190                                            Agent 1-3                                                                     Treating  70          30       220                                            Agent 1-4                                                                     Treating  70          30       250                                            Agent 1-5                                                                     Comparative                                                                             100         --       --                                             Agent 1-1                                                                     ______________________________________                                    

50 g of fly ash containing a large amount of lead, that had beendischarged from a city garbage incineration system, were kneaded with100 g of any one of the above-mentioned treating agents and 30 g ofwater and then cured for 7 days to be solidified. Afterwards, thethus-formed cakes were tested by a lead release test stipulated inNotification No. 13 of the Environment Agency of Japan (the same shallapply hereinunder), on the basis of which the effect of each of thesetreating agents for making the waste harmless was determined. The testresults obtained are shown in Table 8 below, which additionally containsthe amount of lead released from the fly ash to which only ordinaryportland cement (comparative treating agent) was added as the treatingagent (comparative example 1-1), the amount of lead released from thenon-treated fly ash (comparative example 1-2) and the amount of lead asregulated in Japan.

                  TABLE 8                                                         ______________________________________                                        Result of Test for Release of Lead                                                                Amount of                                                             Treating                                                                              Lead Released                                                         Agent Used                                                                            (mg/liter)                                                ______________________________________                                        Example 1-1   Treating  0.88                                                                Agent 1-1                                                       Example 1-2   Treating  0.59                                                                Agent 1-2                                                       Example 1-3   Treating  0.56                                                                Agent 1-3                                                       Example 1-4   Treating  0.45                                                                Agent 1-4                                                       Example 1-5   Treating  0.29                                                                Agent 1-5                                                       Comparative   Comparative                                                                             0.96                                                  Example 1-1   Agent 1-1                                                       Comparative   Non-treated                                                                             25                                                    Example 1-2   Control                                                         Regulated     --        <3                                                    Value                                                                         ______________________________________                                    

The test results shown in Table 8 above indicate that the waste-treatingagents of the present invention, each containing, as a solid acid,activated clay that had been processed to have a specific surface areaof 150 m² /g or more, have a better effect for stabilizing heavy metalsthan the conventional cement.

EXAMPLE 2

80 parts by weight of ordinary portland cement (produced by Ube CementCo.) were mixed with, as a solid acid, 20 parts by weight of one ofaluminium sulfate (produced by Wako Pure Chemicals Co.), aluminiumphosphate (produced by Wako Pure Chemicals Co.), alum (produced by WakoPure Chemicals Co.), aluminium silicate (produced by Wako Pure ChemicalsCo.) and tannin (produced by Wako Pure Chemicals Co.) to prepare awaste-treating agent of the present invention. As a comparative agent,used was ordinary portland cement. The compositions of the treatingagents thus prepared are shown in Table 9 below.

                  TABLE 9                                                         ______________________________________                                        Compositions of Treating Agents                                                         Cement (parts                                                                             Solid Acid  Solid                                       Type      by weight)  (parts by weight)                                                                         Acid Used                                   ______________________________________                                        Treating Agent                                                                          80          20          Aluminium                                   2-1                               Sulfate                                     Treating Agent                                                                          80          20          Aluminium                                   2-2                               Phosphate                                   Treating Agent                                                                          80          20          Alum                                        2-3                                                                           Treating Agent                                                                          80          20          Aluminium                                   2-4                               Silicate                                    Treating Agent                                                                          80          20          Tannin                                      2-5                                                                           Comparative                                                                             100         --          --                                          Agent 2-1                                                                     ______________________________________                                    

2 g of lead chloride were added to 18 ml of pure water and fullystirred, and 45 g of one of the above-mentioned treating agents wereadded thereto, kneaded and cured for 7 days. Afterwards, the thus-curedcakes were treated by a lead release test stipulated in Notification No.13 of the Environment Agency, on the basis of which the effect of eachof these treating agents for making the waste harmless was determined.The test results obtained are shown in Table 10 below, whichadditionally contains the amount of lead released from the lead chloridesolution to which only ordinary portland cement was added as thetreating agent (comparative example 2-1).

                  TABLE 10                                                        ______________________________________                                        Results of Test for Release of Lead                                                      Treating                                                                              Amount of Lead                                                        Agent Used                                                                            Released (mg/liter)                                        ______________________________________                                        Example 2-1  Treating  <0.1                                                                Agent 2-1                                                        Example 2-2  Treating  <0.1                                                                Agent 2-2                                                        Example 2-3  Treating  <0.1                                                                Agent 2-3                                                        Example 2-4  Treating  <0.1                                                                Agent 2-4                                                        Example 2-5  Treating  <0.1                                                                Agent 2-5                                                        Comparative  Comparative                                                                             21                                                     Example 2-1  Agent 2-1                                                        Regulated    --        <3                                                     Value                                                                         ______________________________________                                    

The test results shown in Table 10 above indicate that thewaste-treating agents of the present invention, containing, as a solidacid, any of aluminium sulfate, aluminium phosphate, aluminium silicate,alum and a polyaniline compound, tannin, have a better effect forstabilizing heavy metals than the conventional cement.

EXAMPLE 3

A cation-exchange resin (Dowex 50W-X-8; produced by Dow Chemical Co.)was used as the treating agent (3-1). An anion-exchange resin (Dowex1-X-8; produced by Dow Chemical Co.) was used as the comparative agent(3-1) for a comparative example.

1400 g of distilled water were added to 140 g of lead-containingalkaline fly ash, that had been discharged from a city garbageincineration system, and shaken well. The supernatant thus separated onthe resulting mixture was filtered to obtain an extract. 0.2 g of theabove-mentioned treating agent were added to 200 g of the extract andshaken for 1 hour. Then, the supernatant thus separated was filtered andthe lead concentration in the resulting filtrate was measured. Theresults obtained are shown in Table 11 below, which additionallycontains the lead concentration in the filtrate that had been obtainedin the same manner as above while using comparative agent (3-1) for thecomparative example and also the lead concentration in the non-treatedextract.

                  TABLE 11                                                        ______________________________________                                        Results of Treating of Fly Ash with Ion-Exchange Resin                                            Lead                                                              Ion-Exchange                                                                              Concentration                                                     Resin       (mg/liter) pH                                             ______________________________________                                        Example 3-1                                                                             Cation-Exchange                                                                             83         12.5                                                 Resin                                                               Comparative                                                                             Anion-Exchange                                                                              110        12.5                                       Example 3-1                                                                             Resin                                                               Comparative                                                                             Non-treated   110        12.5                                       Example 3-2                                                                             Control                                                             ______________________________________                                    

It is generally known that lead exists as its anion (plumbite ion) in analkaline range. However, as is obvious from Table 11 above, the leadconcentration in the extract from fly ash that had been treated with thecation-exchange resin was lower than that in the non-treated extract.However, the lead concentration in the extract from fly ash that hadbeen treated with the anion-exchange resin was the same as that in thenon-treated extract. From these, it is known that the cation-exchangeresin which was used as a solid acid has an excellent effect ofstabilizing heavy metals.

EXAMPLE 4

80 parts by weight of ordinary portland cement (produced by Ube CementCo.) were mixed with 20 parts by weight of potassium sulfate (producedby Wako Pure Chemicals Co.) or calcium carbonate (produced by Wako PureChemicals Co.) to prepare a treating agent. 15 g of this treating agentwere added to 50 g of a lead-containing, alkaline fly ash dischargedfrom a city garbage incineration system and kneaded along with 30 g ofwater. The resulting blend was cured for 7 days to be solidified. As acomparative example, 15 g of ordinary portland cement were added to 50 gof the same fly ash as above and kneaded along with 30 g of water, andthe resulting blend was cured and solidified in the same manner asabove. Afterwards, the thus-formed cakes were tested by a metal releasetest stipulated in Notification No. 13 of the Environment Agency, on thebasis of which the effect of each of these treating agents for makingthe waste harmless was comparatively determined. The test resultsobtained are shown in Table 12 below, which additionally lists theamount of lead as regulated in Japan.

                  TABLE 12                                                        ______________________________________                                        Results of Test for Release of Lead                                                            Content of                                                                    Solid Acid in                                                                           Amount of                                                  Solid Acid                                                                             Treating  Lead Released                                              Used     Agent (%) (mg/liter)                                         ______________________________________                                        Example 4-1                                                                             Potassium  20        0.13                                                     Sulfate                                                             Example 4-2                                                                             Calcium    20        0.12                                                     Carbonate                                                           Comparative                                                                             Cement      0        3.3                                            4-1                                                                           Regulated --         --        3                                              Value                                                                         ______________________________________                                    

The results in Table 12 above indicate that the amount of lead releasedwas effectively lowered to below the regulated value when the treatingagents of the present invention were used, although such was impossiblewhen only cement was used. These results support the effect of thewaste-treating agents of the present invention and the effect of themethod of treating waste with these agents.

EXAMPLE 5

60 parts by weight of ordinary portland cement (produced by Ube CementCo.) were mixed with 40 parts by weight of aluminium oxide (produced byWako Pure Chemicals Co.) to prepare a treating agent. This treatingagent was added to 50 g of a lead-containing, alkaline fly ashdischarged from a city garbage incineration system and kneaded alongwith 30 g of water. The resulting blend was cured for 7 days and wasthus solidified. As a comparative example, 5 g or 15 g of ordinaryportland cement were added to 50 g of the same fly ash as above andkneaded along with 30 g of water, and the resulting blend was cured andsolidified in the same manner as above. Afterwards, the thus-formedcakes were tested by a metal release test stipulated in Notification No.13 of the Environment Agency, on the basis of which the effect of eachof these treating agents for making the waste harmless was comparativelydetermined. The test results obtained are shown in Table 13 below, whichadditionally lists the amount of lead released from the non-treated flyash and the amount of lead as regulated in Japan.

                  TABLE 13                                                        ______________________________________                                        Results of Test for Release of Lead                                                                 Amount of Lead                                                     Amount of Treating                                                                       Released                                                           Agent Added (g)                                                                          (mg/liter)                                              ______________________________________                                        Non-treated  --           91                                                  Control                                                                       Example 5-1  2.5          35                                                  Example 5-2  5            31                                                  Example 5-3  10           15                                                  Example 5-4  15           <0.1                                                Comparative  5            45                                                  Example 5-1                                                                   Comparative  15           7.7                                                 Example 5-2                                                                   Regulated Value                                                                            --           3                                                   ______________________________________                                    

The results in Table 13 above indicate that the amount of lead releasedwas effectively lowered to below the regulated value when the treatingagents of the present invention were used, although such was impossiblewhen only cement was used. These results support the effect of thewaste-treating agents of the present invention and the effect of themethod of treating waste with these agents.

EXAMPLE 6

Treating agents (6-1) to (6-5) were prepared by mixing the componentsshown in Table 14 below were prepared.

                  TABLE 14                                                        ______________________________________                                        Compositions of Treating Agents (wt. %)                                       Treating             Aluminium Aluminium                                      Agent    Cement      Sulfate   Silicate                                       ______________________________________                                        Treating 50          50        0                                              Agent 6-1                                                                     Treating 80          20        0                                              Agent 6-2                                                                     Treating 50          0         50                                             Agent 6-3                                                                     Treating 40          30        30                                             Agent 6-4                                                                     Treating 30          35        35                                             Agent 6-5                                                                     ______________________________________                                    

To 50 g of each of two kinds of high-alkaline fly ash A (lead content:0.9% by weight) and high-alkaline fly ash B (lead content: 0.2% byweight), both having been discharged from a city garbage incinerationsystem, added was one of the above-mentioned treating agents (6-1) to(6-5) in the amount as indicated in Table 15 below. These were kneadedalong with 25 g of water, and the resulting blends were cured for 7 daysand were thus solidified. The thus-formed cakes were tested by a metalrelease test stipulated in Notification No. 13 of the EnvironmentAgency, and the test results are shown in Table 15. The same process asabove was repeated, except that 15 g of ordinary portland cement(produced by Ube Cement Co.) were added to each of the above-mentionedfly ashes A and B. The resulting cakes and non-treated fly ashes A and Bwere tested in the same manner as above and the test results are shownin Table 15 as comparative examples. The aluminium sulfate and thealuminium silicate used herein are standard chemicals (produced by WakoPure Chemicals Co.).

                  TABLE 15                                                        ______________________________________                                        Results of Test for Release of Lead                                                      Treatig Agent                                                                             Amount of                                                                    Amount   Lead                                           Type of               Added    Released                                       Fly Ash      Type     (g)      (mg/liter)                                                                           pH                                      ______________________________________                                        Example 6-1                                                                           A        Treating 15     0.1    11.2                                                   Agent 6-1                                                    Example 6-2                                                                           B        Treating 15     1.5    12.7                                                   Agent 6-2                                                    Example 6-3                                                                           B        Treating 15     0.2    12.5                                                   Agent 6-3                                                    Example 6-4                                                                           B        Treating 15     0.1    12.4                                                   Agent 6-4                                                    Example 6-5                                                                           B        Treating 15     <0.1   12.3                                                   Agent 6-5                                                    Comparative                                                                           A        Cement   15     13     12.5                                  Example 6-1                                                                   Comparative                                                                           B        Cement   7.5    3.6    12.3                                  Example 6-2                                                                   Comparative                                                                           B        Cement   15     1.7    12.8                                  Example 6-3                                                                   Comparative                                                                           A          --     --     --     12.7                                  Example 6-4                                                                   Comparative                                                                           B          --     --     --     13.0                                  Example 6-5                                                                   ______________________________________                                    

Comparing the test results in Examples (6-1) to (6-6) with those inComparative Examples (6-1) to (6-5), it is known that the release oflead was more effectively inhibited by the use of the treating agents ofthe present invention while the amount of lead released was somewhatlowered even by the treatment with only cement. These results supportthe effect of the waste-treating agents of the present invention and theeffect of the method of treating waste with these agents.

EXAMPLE 7

60 parts by weight of ordinary portland cement (produced by Ube CementCo.) were mixed with 10 parts by weight of aluminium silicate (producedby Wako Pure Chemicals Co.) to prepare a treating agent (7-1). Atreating agent (7-2) was prepared in the same manner as above, exceptthat the aluminium silicate was replaced by synthetic silicon dioxide(produced by Shionogi & Co.). To 50 g of each of fly ash A and fly ashC, both having been discharged from a city garbage incineration system,and fly ash B that had been discharged from an industrial wasteincineration system, added was each of these treating agents. These werekneaded along with 30 g of water, and the resulting blends were curedfor 7 days and were thus solidified. As comparative examples, ordinaryportland cement was added to 50 g of each of the above-mentioned flyashes, and these were kneaded along with 30 g of water, then cured andsolidified in the same manner as above. Afterwards, the thus-formedcakes were tested by a metal release test stipulated in Notification No.13 of the Environment Agency, on the basis of which the effect of eachof these treating agents for making the waste harmless was comparativelydetermined. The test results obtained are shown in Table 16 below, whichadditionally lists the amount of metal released from each of thenon-treated fly ashes.

                                      TABLE 16                                    __________________________________________________________________________                        Amount                                                              Treating Agent                                                                          of                                                                       Amount                                                                             Water                                                                             Amount of Metal                                       Type of        Added                                                                              Added                                                                             Released (mg/liter)                                   Fly Ash   Type (%)  (g) Pb  Zn  Cd                                            __________________________________________________________________________    Example 7-1                                                                         7-A Treating                                                                           10   42  0.85                                                                              <0.1                                                                              --                                            Example 7-2                                                                             Agent 7-1                                                                          20   42  0.46                                                                              <0.1                                                                              --                                            Example 7-3                                                                             Treating                                                                           10   42  0.76                                                                              <0.1                                                                              --                                            Example 7-4                                                                             Agent 7-2                                                                          20   46  0.31                                                                              <0.1                                                                              --                                            Comparative                                                                             Cement                                                                             20   42  1.2 <0.1                                                                              --                                            Example 7-1                                                                   Comparative                                                                             Kneaded   42  9.1 0.79                                                                              --                                            Example 7-2                                                                             only with                                                                     water                                                               Example 7-5                                                                         7-B Treating                                                                           10   21  ND  0.19                                                                              <0.001                                        Example 7-6                                                                             Agent 7-1                                                                          20   24  ND  <0.1                                                                              <0.001                                        Example 7-7                                                                             Treating                                                                           10   24  ND  0.13                                                                              <0.001                                        Example 7-8                                                                             Agent 7-2                                                                          20   27  ND  <0.1                                                                              <0.001                                        Comparative                                                                             Cement                                                                             20   21  ND  0.97                                                                              <0.08                                         Example 7-3                                                                   Comparative                                                                             Kneaded only with                                                                       21  0.62                                                                              1.6 0.1                                           Example 7-4                                                                             Water                                                               Example 7-9                                                                         7-C Treating                                                                           10   30  0.18                                                                              <0.1                                                                              --                                            Example   Agent 7-1                                                                          20   30  ND  <0.1                                                                              --                                            7-10                                                                          Example   Treating                                                                           10   30  0.12                                                                              <0.1                                                                              --                                            7-11      Agent 7-2                                                           Example        20   33  ND  <0.1                                                                              --                                            7-12                                                                          Comparative                                                                             Cement                                                                             20   30  3.1 <0.1                                                                              --                                            Example 7-5                                                                   Comparative                                                                             Kneaded only with                                                                       30  0.35                                                                              <0.1                                                                              --                                            Example 7-6                                                                             Water                                                               __________________________________________________________________________

From the results in Table 16 above, it is obvious that the combinationof cement and a solid acid, aluminium silicate or silicon dioxide, giveshighly-efficient waste-treating agents.

EXAMPLE 8

Aluminium silicate (1) (specific surface area: 500 m² /g) shown in Table2 above was used as the treating agent (8-1). 50 g of fly ash containinga large amount of lead (amount of lead released from the non-treated flyash: 130 mg/liter), that had been discharged from a city garbageincineration system, were kneaded with 6 g of the treating agent (8-1)and 30 g of water, and the resulting blend was cured for 7 days and wasthus solidified. Afterwards, the thus-formed cake was tested by a leadrelease test stipulated in Notification No. 13 of the EnvironmentAgency, on the basis of which the effect of the treating agent formaking the waste harmless was determined. The test results obtained areshown in Table 17 below. Using 6 g of aluminium silicate (7) (specificsurface area: 100 m² /g) and 6 g of aluminium silicate (8) (specificsurface area: 110 m² /g), both shown in Table 2 above as comparativesamples, the same process and the same test as above were repeated ascomparative examples (8-1) and (8-2), respectively, and the amount oflead released was measured in both comparative examples. Table 17 belowadditionally shows the amount of lead released from the non-treated flyash and the amount of lead as regulated in Japan.

                  TABLE 17                                                        ______________________________________                                        Results of Test for Release of Lead                                                    Treating Agent                                                                        Specific          Amount of                                                   Surface   Amount  Lead                                                        Area      Added   Released                                            Type    (m.sup.2 /g)                                                                            (g)     (mg/liter)                                 ______________________________________                                        Example 8-1                                                                              Treating  500       6     0.84                                                Agent 8-1                                                          Comparative                                                                              Comparative                                                                             100       6     9.8                                      Example 8-1                                                                              Treating                                                                      Agent 8-1                                                          Comparative                                                                              Comparative                                                                             110       6     24                                       Example 8-2                                                                              Treating                                                                      Agent 8-2                                                          Non-treated                                                                              --        --        --    130                                      Control                                                                       Regulated  --        --        --    <3                                       Value                                                                         ______________________________________                                    

From the test results shown in Table 17 above, it is known that treatingagent (8-1) of the present invention has an excellent effect ofpassivating and sequestering lead. When aluminium silicate (7) andaluminium silicate (8) having a small specific surface area were used astreating agents, the amount of lead released from the fly ash treatedtherewith could not be lowered to below the regulated value. As opposedto these, when aluminium silicate (1) having a large specific surfacearea was used (Example 8-1), the amount of lead released from the flyash treated therewith was lowered to below the regulated value.

EXAMPLE 9

Aluminium silicate (1) (content of four-coordinate aluminium atoms: 79.8%) shown in Table 2 above was used as the treating agent (9-1). 50 g offly ash containing a large amount of lead (lead content: 2000 mg/dryweight, CaO content: 41.4%), that had been discharged from a citygarbage incineration system, were kneaded with a pre-determined amount(1 g, 2 g, 4 g, 6 g, 8 g) of the treating agent (9-1) and 30 g of water,and the resulting blends were cured for 7 days and were thus solidified.Afterwards, the thus-formed cakes were tested by a lead release teststipulated in Notification No. 13 of the Environment Agency, on thebasis of which the effect of treating agent for making the wasteharmless was determined. The test results obtained are shown in Table 18below. As comparative examples, each of ordinary cement (ComparativeExample 9-1) and fly ash cement (Comparative Example 9-2) was added, asa treating agent, to 10 g of the same fly ash as above, and the amountof lead released from the thus-treated fly ash was measured in bothcases in the same manner as above. The test results are shown in Table18 below, which additionally lists the amount of lead released from thenon-treated fly ash and the amount of lead as regulated in Japan.

                  TABLE 18                                                        ______________________________________                                        Results of Test for Release of Lead                                                  Treating Amount                                                                      Content of                                                                    Four-       Amount  Amount of                                                 coordinate Al                                                                             Added   Lead Released                                      Type   Atoms (%)   (%)     (mg/liter)                                  ______________________________________                                        Example 9-1                                                                            Treating 79.8        1     30                                        Example 9-2                                                                            Agent 9-1            2     15                                        Example 9-3                                                                            (aluminum            4     3.7                                       Example 9-4                                                                            silicate (1)         6     0.75                                      Example 9-5                   8     <0.1                                      Comparative                                                                            Ordinary --          10    5.8                                       Example 9-1                                                                            Cement                                                               Comparative                                                                            Fly Ash  --          10    4.7                                       Example 9-2                                                                            Cement                                                               Non-treated                                                                              --     --          --    91                                        Control                                                                       Regulated                                                                                --     --          --    <3                                        Value                                                                         ______________________________________                                    

From the test results shown in Table 18 above, it is known that treatingagent (9-1) of the present invention has an excellent effect ofpassivating and sequestering lead. When ordinary cement and fly ashcement were used as treating agents, the amount of lead released fromthe fly ash treated therewith could not be lowered to below theregulated value even though 10 g of the treating agent were added to 50g of fly ash. As opposed to these, when treating agent (9-1) of thepresent invention was used, the amount of lead released from the fly ashtreated therewith was lowered to below 0.1 mg/liter (detectable limit)although the amount of the treating agent added was smaller than that ofthe comparative agent added.

Aluminium silicate (9) (content of four-coordinate aluminium atoms: 37%)shown in Table 2 above was kneaded with 50 g of the same fly ash asabove and 30 g of water, then the resulting blend was cured for 7 daysand was thus solidified. Afterwards, the thus-formed cakes were testedby a lead release test stipulated in Notification No. 13 of theEnvironment Agency, on the basis of which the effect of the treatingagent for making the waste harmless was determined. The test resultsobtained are shown in Table 19 below.

                  TABLE 19                                                        ______________________________________                                        Results of Test for Release of Lead                                                  Treating Amount                                                                      Content of                                                                    Four-       Amount  Amount of                                                 coordinate Al                                                                             Added   Lead Released                                      Type   Atoms (%)   (%)     (mg/liter)                                  ______________________________________                                        Comparative                                                                            Compara- 37.0        1     70                                        Example 9-3                                                                            tive                                                                 Comparative                                                                            Agent 9-1            2     48                                        Example 9-4                                                                            (aluminum                                                            Comparative                                                                            silicate (9)         4     30                                        Example 9-5                                                                   Comparative                   6     14                                        Example 9-6                                                                   Comparative                   8     3.1                                       Example 9-7                                                                   Non-treated                                                                              --     --          --    91                                        Control                                                                       Regulated                                                                                --     --          --    <3                                        Value                                                                         ______________________________________                                    

Comparing the results in Table 19 and those in Table 18, it is knownthat the lead-stabilizing ability of comparative agent (9-1) (aluminiumsilicate (9) having a four-coordinate Al atom content of 37% of all Alatoms) is lower than that of treating agent (9-1) (aluminium silicate(1) having a four-coordinate Al atom content of 79.8% of all Al atoms).Precisely, the amount of lead released from the fly ash treated withcomparative agent (9-1) was higher than that of lead released from thefly ash treated with treating agent (9-1) when the amounts of theseagents used were the same. When 8 g of treating agent (9-1) were addedto 50 g of fly ash, the amount of lead released from the thus-treatedfly ash was lowered to below the detectable limit. However, when 8 g ofcomparative agent (9-1) were added to the same, the amount of leadreleased from the thus-treated fly ash was not lowered to below theregulated value. From these results, it is known that the aluminiumsilicate having a larger four-coordinate Al atom content has a largerheavy-metal-stabilizing capacity.

EXAMPLE 10

Aluminium silicates (1), (2), (3) and (4) shown in Table 2 above (allhaving a four-coordinate Al atom content of more than 50% of all Alatoms) were used as treating agent (10-1), treating agent (10-2),treating agent (10-3) and treating agent (10-4), respectively. 50 g offly ash containing a large amount of lead (amount of lead released fromthe non-treated fly ash: 47 mg/liter), that had been discharged from acity garbage incineration system, were kneaded with 5 g of each oftreating agents (10-1) to (10-4) and 30 g of water, and the resultingblends were cured for 7 days and were thus solidified. Afterwards, thethus-formed cakes were tested by a lead release test stipulated inNotification No. 13 of the Environment Agency, on the basis of which theeffect of the treating agents for making the waste harmless wasdetermined. The test results obtained are shown in Table 20 below. 5 gof aluminium silicate (9) shown in Table 2 above were added, ascomparative agent (10-1), to 50 g of the same fly ash as above, and thesame process and the same test as above were repeated as a comparativeexample. The test result obtained is also shown in Table 20.

                  TABLE 20                                                        ______________________________________                                        Results of Test for Release of Lead                                                  Treating Agent                                                                        Content of                                                                    Four-                                                                         coordinate                                                                              Amount  Amount of                                                   Al Atoms  Added   Lead Released                                       Type    (%)       (g)     (mg/liter)                                   ______________________________________                                        Example 10-1                                                                           Treating  79.8      1     <0.01                                               Agent 10-1                                                           Example 10-2                                                                           Treating  84.0      5     <0.01                                               Agent 10-2                                                           Example 10-3                                                                           Treating  77.6      5     0.01                                                Agent 10-3                                                           Example 10-4                                                                           Treating  79.0      5     <0.01                                               Agent 10-4                                                           Comparative                                                                            Comparative                                                                             37.0      5     0.40                                       Example 10-1                                                                           Agent 10-1                                                           Non-treated                                                                              --      --        --    47                                         Control                                                                       ______________________________________                                    

From the test results shown in Table 20 above, it is known that treatingagents (10-1) to (10-4) of the present invention have an excellenteffect of passivating and sequestering lead. In this experiment, theprecision of the analysis was improved so as to have a detectable limitof 0.01 mg/liter. Even under the severe measurement conditions of thisexperiment, the lead released from the fly ash treated with any one oftreating agents (10-1), (10-2) or (10-4) of this invention was loweredto below the detectable limit and that released from the fly ash treatedwith treating agent (10-3) of this invention was lowered to 0.01mg/liter. As opposed to these, however, the amount of lead released fromthe fly ash treated with comparative agent (10-1) (aluminium silicate(9)) was 0.40 mg/liter, which is not lower than 40 times that of leadreleased from the fly ash treated with any one of treating agents (10-1)to (10-4) of this invention.

EXAMPLE 11

40 parts by weight of any one of aluminium silicate (1), (2), (5) and(6), all shown in Table 2 above, were added to 60 parts by weight ofordinary cement and sufficiently mixed to prepare treating agents (11-1)to (11-4), respectively, as shown in Table 21 below.

                  TABLE 21                                                        ______________________________________                                        Compositions of Treating Agents                                                             Specific   Amount of                                                          Surface Area                                                                             Aluminium Amount of                                  Type of       of Aluminium                                                                             Silicate  Cement                                     Aluminium     Silicate   (parts by (parts by                                  Silicate      (m.sup.2 /g)                                                                             weigh)    weight)                                    ______________________________________                                        Treating                                                                              Aluminium 500        40      60                                       Agent 11-1                                                                            Silicate (1)                                                          Treating                                                                              Aluminium 250                                                         Agent 11-2                                                                            Silicate (2)                                                          Treating                                                                              Aluminium 250                                                         Agent 11-3                                                                            Silicate (5)                                                          Treating                                                                              Aluminium 250                                                         Agent 11-4                                                                            Silicate (6)                                                          ______________________________________                                    

50 g of fly ash containing a large amount of lead, that had beendischarged from a city garbage incineration system, were kneaded with apre-determined amount of any one of treating agents (11-1) to (11-4) and30 g of water, and the resulting blends were cured for 7 days and werethus solidified. Afterwards, the thus-formed cakes were tested by a leadrelease test stipulated in Notification No. 13 of the EnvironmentAgency, on the basis of which the effect of the treating agents formaking the waste harmless was determined. The test results obtained areshown in Table 22 below. As a comparative example, ordinary cement wasused as a treating agent, and the amount of lead released from thethus-treated fly ash was measured and shown in Table 22 below, whichadditionally lists the amount of lead released from the non-treated flyash.

                  TABLE 22                                                        ______________________________________                                        Results of Test for Release of Lead                                                  Treating Agent                                                                       Surface Area                                                                  of Aluminium                                                                  Silicate per         Amount of                                                Gram of      Amount  Lead                                                     Treating     Added   Released                                          Type   Agent (m.sup.2)                                                                            (g)     (mg/liter)                                 ______________________________________                                        Example 11-1                                                                           Treating 200          2.5   1.1                                      Example 11-2                                                                           Agent                 5.0   0.5                                      Example 11-3                                                                           11-1                  7.5   0.3                                      Example 11-4                   10.0  0.1                                      Example 11-5                   12.5  <0.1                                     Example 11-6                   15.0  <0.1                                     Example 11-7                                                                           Treating 100          7.5   0.4                                               Agent                                                                         11-2                                                                 Example 11-8                                                                           Treating 100          7.5   0.5                                               Agent                                                                         11-3                                                                 Example 11-9                                                                           Treating 100          7.5   0.5                                               Agent                                                                         11-4                                                                 Comparative                                                                            Ordinary --           7.5   0.9                                      Example 11-1                                                                           Cement                                                               Non-treated                                                                             --      --           --    27                                       Control                                                                       ______________________________________                                    

From the test results shown in Table 22 above, it is known that treatingagents (11-1) to (11-4) of the present invention have an excellenteffect of preventing the release of lead from the fly ash treatedtherewith. Precisely, even when a smaller amount of treating agent(11-1) was added to fly ash (Example 11-2), than the amount of ordinarycement added thereto, the amount of lead released from the fly ashtreated therewith was lower than that of lead released from the fly ashtreated with ordinary cement (Comparative Example 11-1). When the sameamount (7.5 g--Example 11-3) of treating agent (11-1) was added to flyash, as the amount of ordinary cement added thereto (Comparative Example11-1), the amount of lead released from the fly ash treated therewithwas lower by 1/3 than that of lead released from the fly ash treatedwith ordinary cement. Regarding the other treating agents, when the sameamount of any one of treating agents (11-2) to (11-4) was added to flyash, as the amount of ordinary cement added thereto, the amount of leadreleased from the fly ash treated therewith was lower than that of leadreleased from the fly ash treated with ordinary cement. Comparingtreating agents (11-1) to (11-4) with each other, it is known thattreating agent (11-1) containing aluminium silicate having a largerspecific surface area has a higher effect of preventing the release oflead from the fly ash treated therewith.

EXAMPLE 12

35 parts by weight of aluminium silicate (1) (specific surface area: 500m² /g) shown in Table 2 above were added to 65 parts by weight of cementshown in Table 23 below and well mixed to prepare treating agent (12-1),treating agent (12-2) and treating agent (12-3), as shown Table 23.

                  TABLE 23                                                        ______________________________________                                        Compositions of Treating Agents                                                             Specific   Amount of                                                          Surface Area                                                                             Aluminium Amount of                                  Type of       of Aluminium                                                                             Silicate  Cement                                     Alulminium    Silicate   (parts by (parts by                                  Silicate      (m.sup.2 /g)                                                                             weight)   weight)                                    ______________________________________                                        Treating                                                                              Ordinary  500        35      65                                       Agent 12-1                                                                            Cement                                                                Treating                                                                              High-early-                                                           Agent 12-2                                                                            strength                                                                      Cement                                                                Treating                                                                              Slag Cement                                                           Agent 12-3                                                                    ______________________________________                                    

50 g of fly ash containing a large amount of lead, that had beendischarged from a city garbage incineration system, were kneaded with apre-determined amount of any one of treating agent (12-1), treatingagent (12-2) and treating agent (12-3), along with 30 g of water, andthe resulting blends were cured for 7 days and were thus solidified.Afterwards, the thus-formed cakes were tested by a lead release teststipulated in Notification No. 13 of the Environment Agency, on thebasis of which the effect of the treating agents for making the wasteharmless was determined. The test results obtained are shown in Table 24below. As a comparative example, ordinary cement only was added to flyash, as a treating agent, and the amount of lead released from thethus-treated fly ash was measured and shown in Table 24 below, whichadditionally lists the amount of lead released from the non-treated flyash and the amount of lead as regulated in Japan.

                  TABLE 24                                                        ______________________________________                                        Results of Test for Release of Lead                                                  Treating Agent                                                                        Surface Area                                                                  of Aluminium                                                                  Silicate per        Amount of                                                 Gram of     Amount  Lead                                                      Treating    Added   Released                                          Type    Agent (m.sup.2)                                                                           (g)     (mg/liter)                                 ______________________________________                                        Example 12-1                                                                           Treating  175         10    0.8                                               Agent 12-1                                                           Example 12-2                                                                           Treating                    0.7                                               Agent 12-2                                                           Example 12-3                                                                           Treating                    1.5                                               Agent 12-3                                                           Comparative                                                                            Ordinary  --          10    5.8                                      Example 12-1                                                                           Cement                                                               Non-treated                                                                             --       --          --    100                                      Control                                                                       Regulated                                                                               --       --          --    <3                                       Value                                                                         ______________________________________                                    

From the test results shown in Table 24 above, it is known that treatingagents (12-1), (12-2) and (12-3) of the present invention have anexcellent effect of preventing the release of lead from the fly ashtreated therewith. Precisely, since these treating agents of the presentinvention were comprised of aluminium silicate having a high specificsurface area and cement, the amount of lead released from the fly ashtreated with any one of these was much lower than that of lead releasedfrom the fly ash treated with ordinary cement only. The kind of cementto be added to aluminium silicate to form the treating agents of thepresent invention is not specifically defined. It is known from theresults in Table 24 above that the effect of the treating agents of thepresent invention is higher than that of cement only, irrespective ofthe kind of cement added to these treating agents.

EXAMPLE 13

Aluminium silicate (1) shown in Table 2 above was added to ordinarycement and well mixed to prepare treating agent (13-1) to treating agent(13-6), as shown in Table 25 below.

                  TABLE 25                                                        ______________________________________                                        Compositions of Treating Agents                                                           Cement (parts by                                                                        Aluminium Silicate                                                  weight)   (parts by weight)                                       ______________________________________                                        Treating Agent 13-1                                                                         60          40                                                  Treating Agent 13-2                                                                         70          30                                                  Treating Agent 13-3                                                                         75          25                                                  Treating Agent 13-4                                                                         80          20                                                  Treating Agent 13-5                                                                         85          15                                                  Treating Agent 13-6                                                                         90          10                                                  ______________________________________                                    

50 g of fly ash containing a large amount of lead, that had beendischarged from a city garbage incineration system, were kneaded with apre-determined amount of any one of treating agents (13-1) to (13-6) and30 g of water, and the resulting blends were cured for 7 days and werethus solidified. Afterwards, the thus-formed cakes were tested by a leadrelease test stipulated in Notification No. 13 of the EnvironmentAgency, on the basis of which the effect of the treating agents formaking the waste harmless was determined. The test results obtained areshown in Table 26 below. As a comparative example, ordinary cement onlywas added to fly ash, as a treating agent, and the amount of leadreleased from the thus-treated fly ash was measured and shown in Table24 below, which additionally has the amount of lead released from thenon-treated fly ash.

                  TABLE 26                                                        ______________________________________                                        Results of Test for Release of Lead                                                  Treating Agent                                                                        Surface Area                                                                  of Aluminium                                                                  Silicate per        Amount of                                                 Gram of     Amount  Lead                                                      Treating    Added   Released                                          Type    Agent (m.sup.2)                                                                           (g)     (mg/liter)                                 ______________________________________                                        Example 13-1                                                                           Treating  200         7.5   1.4                                               Agent 13-1                                                           Example 13-2                                                                           Treating  150         7.5   1.2                                               Agent 13-2                                                           Example 13-3                                                                           Treating  125         7.5   1.3                                               Agent 13-3                                                           Example 13-4                                                                           Treating  100         7.5   1.6                                               Agent 13-4                                                           Example 13-5                                                                           Treating   75         7.5   2.4                                               Agent 13-5                                                           Example 13-6                                                                           Treating   50         7.5   5.1                                               Agent 13-6                                                           Comparative                                                                            Ordinary  --          10    9.8                                      Example 13-1                                                                           Cement                                                               Non-treated                                                                             --       --          --    110                                      Control                                                                       ______________________________________                                    

From the results shown in Table 26 above, it is known that the amount oflead released from the fly ash treated with any one of the treatingagents of the present invention was smaller than that of lead releasedfrom the fly ash treated with ordinary cement only, even though theamount of each of the treating agents of the present invention added tofly ash was smaller than the amount of ordinary cement only addedthereto. In other words, it is known that the treating agents of thepresent invention each containing aluminium silicate having a surfacearea of 50 m² or more per gram of the treating agent have a higherlead-stabilizing effect than ordinary cement.

EXAMPLE 14

Silicon dioxide (1) and (2) shown in Table 3 above were used as treatingagent (14-1) and treating agent (14-2), respectively. 50 g of fly ashcontaining a large amount of lead (amount of lead released from thenon-treated fly ash: 40 mg/liter), that had been discharged from a citygarbage incineration system, were kneaded with 5 g of treating agent(14-1) or treating agent (14-2) along with 30 g of water, and theresulting blends were cured for 9 days and were thus solidified.Afterwards, the thus-formed cakes were tested by a lead release teststipulated in Notification No. 13 of the Environment Agency, on thebasis of which the effect of the treating agents for making the wasteharmless was determined. The test results obtained are shown in Table 27below.

                  TABLE 27                                                        ______________________________________                                        Results of Test for Release of Lead                                                  Treating Agent                                                                        Specific              Amount of                                               Surface Q4      Amount                                                                              Lead                                                    Area    Content Added Released                                        Type    (m.sup.2 /g)                                                                          (%)     (g)   (mg/liter)                               ______________________________________                                        Example 14-1                                                                           Treating  429     75.2  8     <0.1                                            Agent 14-1                                                           Example 14-2                                                                           Treating  165     --    8     <0.1                                            Agent 14-2                                                           Comparative                                                                            Silicon   120     86.7  8     0.25                                   Example 14-1                                                                           Dioxide (5)                                                          Non-treated                                                                             --       --      --    --    40                                     Control                                                                       ______________________________________                                    

From the test results shown in Table 27 above, it is known that thetreating agents of the present invention have an excellent effect ofpassivating and sequestering lead. Precisely, when the silicon dioxidehaving a specific surface area of more than 150 m² /g was used as thetreating agent, the amount of lead released from the fly ash treatedtherewith could be lowered to below the detectable limit. However, whenthe silicon dioxide having a specific surface area of less than 150 m²/g was used as a comparative example, the amount of lead released fromthe fly ash treated therewith was 0.25 mg/liter. The treating agent ofExample 14-1 was silicon dioxide having a Q4 silicon atom content ofless than 85%, while that of Comparative Example 14-1 was silicondioxide having a Q4 silicon atom content of more than 85%.

EXAMPLE 15

50 parts by weight of ordinary portland cement were well mixed with 50parts by weight of either of silicon dioxide (1) and silicon dioxide (3)shown in Table 3 above, to prepare treating agent (15-1) and treatingagent (15-2), respectively. 100 g of fly ash containing a large amountof lead (lead content: 1300 mg/kg, amount of lead released from thenon-treated fly ash: 40 mg/liter), that had been discharged from a citygarbage incineration system, were kneaded with 7.5 g or 15 g of eitherof treating agent (15-1) and treating agent (15-2), along with 30 g ofwater, and the resulting blends were cured for 7 days and were thussolidified. Afterwards, the thus-formed cakes were tested by a leadrelease test stipulated in Notification No. 13 of the EnvironmentAgency, on the basis of which the effect of the treating agents formaking the waste harmless was determined. The test results obtained areshown in Table 28 below. As comparative examples, 15 g of silicondioxide (6) shown in Table 3 above and 15 g of ordinary portland cementwere used as comparative agent (15-1) and comparative agent (15-2),respectively, and these were tested in the same manner as above. Thetest results are also shown in Table 28 below.

                  TABLE 28                                                        ______________________________________                                        Results of Test for Release of Lead                                                  Treating Agent                                                                                Surface                                                                       Area of                                                                       Silicon                                                               Specific                                                                              Dioxide                                                               Surface per Gram                                                              Area of of             Amount of                                              Silicon Treating Amount                                                                              Lead                                                   Dioxide Agent    Added Released                                       Type    (m.sup.2 /g)                                                                          (m.sup.2)                                                                              (g)   (mg/liter)                              ______________________________________                                        Example 15-1                                                                           Treating  429     215    15    <0.1                                  Example 15-2                                                                           Agent 15-1               7.5   0.40                                  Example 15-3                                                                           Treating  237     119    15    0.18                                  Example 15-4                                                                           Agent 15-2               7.5   0.46                                  Comparative                                                                            Comparative                                                                             109      55    15    0.46                                  Example 15-1                                                                           Agent 15-1                                                           Comparative                       7.5   0.96                                  Example 15-2                                                                  Comparative                                                                            Comparative                                                                             --      --     15    1.3                                   Example 15-3                                                                           Agent 15-2                                                           Non-treated                                                                              --      --      --     --    40                                    Control                                                                       ______________________________________                                    

From the test results shown in Table 28 above, it is known that treatingagent (15-1) and treating agent (15-2) of the present invention have anexcellent effect of passivating and sequestering lead. Precisely, it isknown that when silicon dioxide having a specific surface area of morethan 150 m² /g was used as the treating agent, the amount of leadreleased from the fly ash treated therewith was less than 1/2 of theamount of lead released from the fly ash treated with silicon dioxidehaving a specific surface area of less than 150 m² /g and was less than1/10 of the amount of lead released from the fly ash treated withportland cement. When 30% by weight of treating agent (15-1) was addedto fly ash, it was possible to lower the amount of lead released fromthe fly ash treated therewith below the detectable limit. It is alsoknown from these results that the treating agent containing silicondioxide having a larger specific surface area or having a largerspecific surface area per gram of the treating agent has a higher effectof passivating and sequestering lead.

EXAMPLE 16

80 parts by weight of ordinary portland cement were well mixed with 20parts by weight of either of silicon dioxide (1) and silicon dioxide (4)shown in Table 3 above, to prepare treating agent (16-1) and treatingagent (16-2), respectively. 50 g of fly ash containing a large amount oflead (lead content: 1300 mg/kg, amount of lead released from thenon-treated fly ash: 87 mg/liter), that had been discharged from a citygarbage incineration system, were kneaded with 7.5 g of either oftreating agent (16-1) and treating agent (16-2), along with 30 g ofwater, and the resulting blends were cured for 7 days and were thussolidified. Afterwards, the thus-formed cakes were tested by a leadrelease test stipulated in Notification No. 13 of the EnvironmentAgency, on the basis of which the effect of the treating agents formaking the waste harmless was determined. The test results obtained areshown in Table 29 below. As an comparative example, 20 parts by weightof silicon dioxide (5) were mixed with 80 parts by weight of ordinaryportland cement to prepare comparative agent (16-1). Using 15 g of this,the same fly ash as above was treated in the same manner. This wastested in the same manner and the test results are also shown in Table29, which additionally has the amount of lead released from thenon-treated fly ash.

                  TABLE 29                                                        ______________________________________                                        Result of Test for Release of Lead                                                   Treating Agent                                                                        Surface                                                                       Area of                                                                       Silicon                                                                       Dioxide                                                                       per Gram                                                                      of                     Amount of                                              Treating Q4      Amount                                                                              Lead                                                   Agent    Content Added Released                                       Type    (m.sup.2 /g)                                                                           (%)     (g)   (mg/liter)                              ______________________________________                                        Example 16-1                                                                           Treating  86       75.2  7.5   1.4                                            Agent 16-1                                                           Example 16-2                                                                           Treating  48       75.4  7.5   1.6                                            Agent 16-2                                                           Comparative                                                                            Comparative                                                                             24       86.7  7.5   2.1                                   Example 16-1                                                                           Agent 16-1                                                           Non-treated                                                                             --       --       --    --    40                                    Control                                                                       ______________________________________                                    

From the test results shown in Table 29 above, it is known that whensilicon dioxide having a smaller Q4 silicon atom content was used as thetreating agent, the amount of lead released from the fly ash treatedtherewith was smaller. It is also known therefrom that the treatingagent containing silicon dioxide having a surface area of more than 50m² /g, per gram of the treating agent, has a higher effect ofstabilizing lead.

EXAMPLE 17

30 parts by weight of aluminium silicate (1) surface potential (at a pHof 7 or higher): less than -15 mV!, of which the physical properties andthe surface potential have been shown in Table 2 and Table 4 above, wereadded to 70 parts by weight of ordinary portland cement to obtaintreating agent (17-1). 50 g of fly ash containing a large amount of lead(amount of lead released from the non-treated fly ash: 90 mg/liter),that had been discharged from a city garbage incineration system, werekneaded with 10 g of treating agent (17-1) and 30 g of water, and theresulting blend was cured for 7 days and was thus solidified.Afterwards, the thus-formed cake was tested by a lead release teststipulated in Notification No. 13 of the Environment Agency, on thebasis of which the effect of the treating agent for making the wasteharmless was determined. The test results obtained are shown in Table 30below. As an comparative example, 5 g of aluminium silicate (9), ofwhich the physical properties and the surface potential have been shownin Table 2 and Table 5 above, were used as comparative agent (17-1), andthe test results are also shown in Table 30 below, which additionallylists the amount of lead released from the non-treated fly ash and theamount of lead as regulated in Japan.

                  TABLE 30                                                        ______________________________________                                        Result of Test for Release of Lead                                                     Treating Agent Amount of Lead                                                           Amount   Released                                                   Type      Added (g)                                                                              (mg/liter)                                        ______________________________________                                        Example 17-1                                                                             Treating    10       2.3                                                      Agent 17-1                                                         Comparative                                                                              Comparative 10       11                                            Example 17-1                                                                             Agent 17-1                                                         Non-treated                                                                              --          --       90                                            Control                                                                       Regulated  --          --       <3                                            Value                                                                         ______________________________________                                    

From the test results shown in Table 30 above, it is known that treatingagent (17-1) of the present invention has an excellent effect ofpassivating and sequestering lead. Precisely, when treating agent (17-1)was used, the amount of lead released from the fly ash treated therewithwas lowered to below the regulated value. As opposed to this, however,when comparative agent (17-1) containing aluminium silicate (9) having asurface potential of more than -14 mV at a pH of 7 or higher was used,the amount of lead released from the fly ash treated therewith was 11mg/liter which is higher than the regulated value.

EXAMPLE 18

20 parts by weight of aluminium sulfate and 50 parts by weight ofsilicon dioxide (1) surface potential (at a pH of 7 or higher): lessthan -15 mV!, of which the physical properties and the surface potentialhave been shown in Table 3 and Table 6 above, were added to 30 parts byweight of ordinary portland cement to obtain treating agent (18-1). 20parts by weight of aluminium sulfate and 50 parts by weight of aluminiumsilicate (9) were added to 30 parts by weight or ordinary portlandcement to prepare comparative agent (18-1). 50 g of fly ash containing alarge amount of lead (amount of lead released from the non-treated flyash: 40 mg/liter), that had been discharged from a city garbageincineration system, were kneaded with 7.5 g of treating agent (18-1)and 30 g of water, and the resulting blend was cured for 7 days and wasthus solidified. Afterwards, the thus-formed cake was tested by a leadrelease test stipulated in Notification No. 13 of the EnvironmentAgency, on the basis of which the effect of the treating agent formaking the waste harmless was determined. The test results obtained areshown in Table 31 below. As comparative examples, 5 g, 10 g or 15 g ofcomparative agent (18-1) were used, and the test results are also shownin Table 31 below, which additionally lists the amount of lead releasedfrom the non-treated fly ash and the amount of lead as regulated inJapan.

                  TABLE 31                                                        ______________________________________                                        Results of Test for Release of Lead                                                    Treating Agent Amount of Lead                                                           Amount   Released                                                   Type      Added (g)                                                                              (mg/liter)                                        ______________________________________                                        Example 18-1                                                                             Treating    7.5      <0.1                                                     Agent 18-1                                                         Comparative                                                                              Comparative 5        0.95                                          Example 18-1                                                                             Agent 18-1                                                         Comparative            10       0.45                                          Example 18-2                                                                  Comparative            15       0.21                                          Example 18-3                                                                  Non-treated                                                                              --          --       40                                            Control                                                                       Regulated  --          --       <3                                            Value                                                                         ______________________________________                                    

From the test results shown in Table 31 above, it is known that treatingagent (18-1) of the present invention has an excellent effect ofpassivating and sequestering lead. Precisely, when treating agent (18-1)was used, the amount of lead released from the fly ash treated therewithwas lowered to below the detectable limit (0.1 mg/liter). As opposed tothis, however, when comparative agent (18-1) containing aluminiumsilicate (9) having a surface potential of more than -14 mV at a pH of 7or higher was used, the amount of lead released from the fly ash treatedtherewith could not be lowered to below the detectable limit even thoughthe amount of the agent added was increased twice the amount of treatingagent (18-1) of this invention.

EXAMPLE 19

10 parts by weight of aluminium sulfate, 20 parts by weight of aluminiumsilicate (1) shown in Table 2 above and 20 parts by weight of any one ofvarious silicon dioxides shown in Table 3 above were well mixed alongwith 50 parts by weight of ordinary portland cement to obtain treatingagents (19-1) to (19-4) shown in Table 32 below.

                  TABLE 32                                                        ______________________________________                                        Compositions of Treating Agents (parts by weight)                                                    Silicon Dioxide                                        Ordinary     Aluminium Aluminium       Amount                                 Cement       Sulfate   Silicate  Type  Added                                  ______________________________________                                        Treating                                                                              50       10        20      Silicon                                                                             20                                   Agent 19-1                         Dioxide                                                                       (1)                                        Treating                                                                              50       10        20      Silicon                                                                             20                                   Agent 19-2                         Dioxide                                                                       (2)                                        Treating                                                                              50       10        20      Silicon                                                                             20                                   Agent 19-3                         Dioxide                                                                       (3)                                        Treating                                                                              50       10        20      Silicon                                                                             20                                   Agent 19-4                         dioxide                                                                       (4)                                        ______________________________________                                    

50 g of fly ash containing a large amount of lead (amount of leadreleased from the non-treated fly ash: 120 mg/liter), that had beendischarged from a city garbage incineration system, were kneaded with 15g of any one of treating agents (19-1) to (19-4), along with 30 g ofwater, and the resulting blends were cured for 7 days and were thussolidified. Afterwards, the thus-formed cakes were tested by a leadrelease test stipulated in Notification No. 13 of the EnvironmentAgency, on the basis of which the effect of the treating agents formaking the waste harmless was determined. The test results obtained areshown in Table 33 below, which additionally lists the amount of leadreleased from the non-treated fly ash and the amount of lead asregulated in Japan.

                  TABLE 33                                                        ______________________________________                                        Results of Test Release of Lead                                                        Treating Agent                                                                              Amount of Lead                                                           Amount   Released                                                    Type     Added (g)                                                                              (mg/liter)                                         ______________________________________                                        Example 19-1                                                                             Treating   7.5      <0.o1                                                     Agent 19-1                                                         Example 19-2                                                                             Treating   7.5      0.03                                                      Agent 19-2                                                         Example 19-3                                                                             Treating   7.5      0.16                                                      Agent 19-3                                                         Example 19-4                                                                             Treating   7.5      0.03                                                      Agent 19-4                                                         Non-treated                                                                               --        --       120                                            Control                                                                       Regulated   --        --       <3                                             Value                                                                         ______________________________________                                    

From the test results shown in Table 33 above, it is known that thetreating agents of the present invention have an excellent effect ofpassivating and sequestering lead. Precisely, using the treating agentsof the present invention, the amount of lead released from the high-leadfly ash, that releases 120 mg/liter of lead when it is not treated, waslowered to between 1/100 and 1/10 of the regulated value. From theseresults, it is also known that the combination of aluminium silicate andsilicon dioxide gives waste-treating agents which are highly effective.Accordingly, in view of the production costs and the physical properties(bulk density, fluidity) of these treating agents, it is recommended tocombine aluminium silicate and silicon dioxide at any desiredproportion.

EXAMPLE 20

Comparative examples are first mentioned herein. Fly ash that had beendischarged from a city garbage incineration system was collected in abag filter, and this was subjected to a metal release test stipulated inNotification No. 13 of the Environment Agency. The result obtained isshown in Table 34 as Comparative Example 20-1. 15 g of ordinary portlandcement were added to 50 g of the same fly ash as above and kneaded alongwith 30 g of water, and the resulting blend was cured for 7 days and wasthus solidified. This was subjected to a metal release test stipulatedin Notification No. 13 of the Environment Agency, and the resultobtained is shown in Table 34 as Comparative Example 20-2.

Ordinary portland cement (produced by Ube Cement Co.) and aluminiumsulfate (produced by Yashiro Chemical Co.) were mixed at a weight ratioof 50/50 to obtain a treating agent. Two kinds of aluminium sulfate,that had been produced in the same series but as different lots, wereused herein. The results of the test using aluminium sulfate of one lotare shown as Comparative Example 20-3, while those of the test usingaluminium sulfate of the other lot are as Comparative Example 20-4. Thesame metal release test as in Comparative Example 20-2 was carried out,while using any one of the above-mentioned treating agents in place ofcement, and the results obtained are shown in Table 34 below. Toevaluate the caking property of these treating agents, a caking test wascarried out according to the process mentioned below. Precisely, about200 g of each treating agent were put into a 500 ml-plastic containerand left as they were for 5 days or 10 days, while a 5-kg weight wasapplied onto it. Afterwards, the treating agent was taken out from thecontainer and sieved through a 2-mm-mesh sieve, and the amount of thecake (caked treating agent) remained on the sieve was weighed. Thepercentage (%) of the weight of the cake thus measured, relative to theweight of the fresh treating agent, was obtained, from which the cakingproperty of the treating agent tested was evaluated. A treating agenthaving a lower percentage of the cake is better. The test results areshown in Table 34 below.

Comparing the results of Comparative Example 20-3 with those ofComparative Example 20-4, it is known that the caking property ofaluminium sulfate products produced by the same manufacturer indifferent lots significantly varies. This is considered to be because ofthe delicate conditions for production and storage would have aninfluence on the surface condition, etc. of these aluminium sulfateproducts. At present, however, details of the reasons f or this are notclear. In the present Example 20, therefore, aluminium sulfate of thesame lot as that used in Comparative Example 20-4 or, that is, theeasily caking aluminium sulfate was used in order to distinctlydemonstrate the effect of the present invention.

EXAMPLE 20-1 TO EXAMPLE 20-5

Ordinary portland cement (produced by Ube Cement Co.), aluminium sulfate(produced by Yashiro Chemical Co.) and a caking inhibitor were mixed ata ratio of 50/50/10 by weight to prepare treating agents. As the cakinginhibitor, used were silica gel, activated clay, calcium stearate,activated alumina and aluminium stearate, in Examples 20-1 to Examples20-5, respectively. The same metal release test as that in ComparativeExample 20-2 was carried out, using each of these treating agent sprepared above, in place of cement. The test results obtained are shownin Table 34 below. In addition, t he same caking test as that inComparative Examples 20-3 and 20-4 was carried out, using these treatingagents. The test results obtained are shown in Table 34 below.

EXAMPLE 20-6

5 parts by weight of palm oil that had been dissolved in tetrahydrofuranwere mixed with 100 parts by weight of aluminium sulfate, and thetetrahydrofuran was removed from the resulting mixture in vacuum. Thiswas mixed with cement at a ratio of 55/50 by weight to prepare atreating agent. This treating agent was subjected to the same metalrelease test and the same caking test as those mentioned above. The testresults obtained are shown in Table 34.

EXAMPLE 20-7

Ordinary portland cement (produced by Ube Cement Co.), aluminium sulfate(produced by Yashiro Chemical Co.) and calcium stearate were mixed at aratio of 50/50/5 by weight to prepare a treating agent, which wassubjected to the same metal release test and the same caking test asthose mentioned above. The test results obtained are shown in Table 34.

                  TABLE 34                                                        ______________________________________                                        Results of Caking Test and Lead Release Test                                                Result of                                                                     Caking Test (%)                                                                          Amount of                                                    Caking  After    After 10                                                                              Lead Released                                        Inhibitor                                                                             5 days   days    (mg/liter)                                   ______________________________________                                        Comparative                                                                             --        --       --    493                                        Example 20-1                                                                  Comparative                                                                             --        --       --    13                                         Example 20-2                                                                  Comparative                                                                             --         1        3    0.3                                        Example 20-3                                                                  Comparative                                                                             --        98       99    0.3                                        Example 20-4                                                                  Example 20-1                                                                            Silica Gel                                                                              11        8    0.5                                        Example 20-2                                                                            Activated  5        4    0.2                                                  Clay                                                                Example 20-3                                                                            Calcium    4        9    0.4                                                  Stearate                                                            Example 20-4                                                                            Activated  3        5    0.2                                                  Alumina                                                             Example 20-5                                                                            Aluminium 20       95    0.3                                                  Stearate                                                            Example 20-6                                                                            Palm Oil  19       22    0.9                                        Example 20-7                                                                            Calcium   43       96    0.6                                                  Stearate                                                            ______________________________________                                    

The test results of Comparative Example 20-2, Comparative Example 20-3,Comparative Example 20-4 and Examples 20-1 to 20-7 shown in Table 34above demonstrate that the amount of lead released from the fly ashtreated with cement was greatly lowered as compared with that releasedfrom the non-treated fly ash. This, however, is not satisfactory, whilethe amount of lead released from the fly ash treated with any one of thetreating agents of the present invention was lowered to less than 1mg/liter; although this more or less varies depending on the kind andthe amount of the caking inhibitor added thereto. Thus, these verify thesignificance of the addition of the solid acid to the waste-treatingagent to give the ability to inhibit the release of metal from the flyash treated with the agent. (In Comparative Examples 20-3 and 20-4, usedwere treating agents each containing a solid acid. Therefore, therelease of lead from the fly ash treated with each of the agents washighly inhibited in these comparative examples. Since the anti-cakingeffect of the treating agents used is discussed herein as needed, thesecases using these treating agents are intentionally referred to ascomparative examples.) Comparing the results of Comparative Example 20-4where the easily caking aluminium sulfate was used and those of Examples20-1 to 20-7 where the same aluminium sulfate was used, the effect ofthe caking inhibitor in the treating agents of the present invention wasverified by the caking test (anti-caking test). However, the anti-cakingeffect varied, depending on the kind and amount of caking inhibitorused, as is obvious from the comparison between Example 20-3 and Example20-7. From this, it is known that the kind and the amount of the cakinginhibitor to be added to the waste-treating agent of the presentinvention shall be appropriately selected. The results obtained hereinthus demonstrate the effect of the waste-treating agents of the presentinvention of inhibiting the release of heavy metals from the wastetreated therewith and also their anti-caking effect (stability duringstorage). From the results, therefore, these effects of thewaste-treating agents of the present invention have become obvious.

EXAMPLE 21

60 or 70 parts by weight of ordinary portland cement (produced by UbeCement Co.) were mixed with from 10 to 20 parts by weight of one or moreof aluminium silicate having a specific surface area of 500 m² /gmeasured by a BET method, as a solid acid, and, as reducing agents,sodium thiosulfate (produced by Wako Pure Chemicals Co.), allophane(produced by Matsumura Industry Co.) and bentonite (produced by KunimineIndustrial Co.), to prepare the treating agents of the presentinvention. As a comparative example, 80 parts by weight or ordinaryportland cement were mixed with 20 parts by weight of aluminium silicateto prepare comparative agent (21-1). The compositions of thethus-prepared agents are shown in Table 35 below.

                  TABLE 35                                                        ______________________________________                                        Compositions of Treating Agents (parts by weight)                             Kind of                                                                       Treating       Aluminium Sodium                                               Agent  Cement  Silicate  Thiosulfate                                                                           Allophane                                                                            Bentonite                             ______________________________________                                        Treating                                                                             70      20        10      --     --                                    Agent                                                                         21-1                                                                          Treating                                                                             70      20        --      10     --                                    Agent                                                                         21-2                                                                          Treating                                                                             70      20        --      --     10                                    Agent                                                                         21-3                                                                          Treating                                                                             60      20        10      10     --                                    Agent                                                                         21-4                                                                          Treating                                                                             60      20        10      --     10                                    Agent                                                                         21-5                                                                          Treating                                                                             60      20        --      10     10                                    Agent                                                                         21-6                                                                          Treating                                                                             60      20         5      10      5                                    Agent                                                                         21-7                                                                          Compara-                                                                             80      20        --      --     --                                    tive                                                                          Agent                                                                         21-1                                                                          ______________________________________                                    

50 g of fly ash containing a large amount of lead, that had beendischarged from a city garbage incineration system, were kneaded with7.5 g of any one of these treating agents along with 30 g of water, andthe resulting blends were cured for 7 days and were thus solidified.Afterwards, the thus-formed cakes were tested by a lead release teststipulated in Notification No. 13 of the Environment Agency, on thebasis of which the effect of the treating agents for making the wasteharmless was determined. The test results obtained are shown in Table 36below, which additionally lists the amount of lead released from the flyash treated with ordinary cement only as a comparative example, theamount of lead released from the non-treated fly ash and the amount oflead as regulated in Japan.

                  TABLE 36                                                        ______________________________________                                        Results of Test for Release of Lead                                                                  Amount of Lead                                                   Treating Agent                                                                             Released (mg/liter)                                    ______________________________________                                        Example 21-1                                                                              Treating Agent 21-1                                                                          0.43                                               Example 21-2                                                                              Treating Agent 21-2                                                                          0.15                                               Example 21-3                                                                              Treating Agent 21-3                                                                          0.28                                               Example 21-4                                                                              Treating Agent 21-4                                                                          0.12                                               Example 21-5                                                                              Treating Agent 21-5                                                                          0.20                                               Example 21-6                                                                              Treating Agent 21-6                                                                          0.12                                               Example 21-7                                                                              Treating Agent 21-7                                                                          <0.1                                               Comparative Comparative Agent 21-1                                                                       0.66                                               Example 21-1                                                                  Non-treated --             37                                                 Control                                                                       Regulated   --             <3                                                 Value                                                                         ______________________________________                                    

The test results shown in Table 36 above demonstrate that thewaste-treating agents of the present invention each additionallycontaining reducing agent(s), allophane and/or bentonite, in addition tothe solid acid, aluminium silicate, have a further improved effect ofstabilizing the heavy metals.

EXAMPLE 22

5 parts by weight of silica gel (produced by Wako Pure Chemicals Co.)were dispersed in 100 parts by weight of a solution of 100 g/liter of H₃PO₄. After having been stirred, this was filtered to obtain a cake. Thecake was dried at 150° C. to prepare treating agent (22-1). On the otherhand, treating agent (22-2) was prepared in the same manner as in thepreparation of treating agent (22-1), except that sulfuric acid was usedin place of the H₃ PO4 solution. 50 g of fly ash containing a largeamount of lead, that had been discharged from a city garbageincineration system, were kneaded with 5 g, 7.5 g or 10 g of either ofthese treating agents along with 30 g of water, and the resulting blendswere cured for 7 days to be solidified. Afterwards, the thus-formedcakes were tested by a lead release test stipulated in Notification No.13 of the Environment Agency, on the basis of which the effect of thetreating agents for making the waste harmless was determined. The testresults obtained are shown in Table 37 below, which additionally liststhe amount of lead released from the fly ash treated with ordinarycement only as Comparative Example 22-1, the amount of lead releasedfrom the non-treated fly ash and the amount of lead as regulated inJapan.

                  TABLE 37                                                        ______________________________________                                        Results of Test for Release of Lead                                                            Amount of                                                                     Treating   Amount of Lead                                            Treating Agent Add  Released                                                  Agent    (g)         mg/liter!                                        ______________________________________                                        Example 22-1                                                                            Treating   5          2.8                                                     Agent 22-1                                                          Example 22-2                                                                            Treating   7.5        1.4                                                     Agent 22-1                                                          Example 22-3                                                                            Treating   10         0.8                                                     Agent 22-1                                                          Example 22-4                                                                            Treating   5          3.2                                                     Agent 22-2                                                          Example 22-5                                                                            Treating   7.5        1.8                                                     Agent 22-2                                                          Example 22-6                                                                            Treating   10         1.0                                                     Agent 22-2                                                          Comparative                                                                             Cement     10         3.7                                           Example 22-1                                                                  Non-treated                                                                             --         --         53                                            Control                                                                       Regulated --         --         <3                                            Value                                                                         ______________________________________                                    

From the results in Table 37 above, it is known that the treating agentsof the present invention have an excellent effect of passivating andsequestering lead. Precisely, the amount of lead released from the flyash treated with any one of the treating agents of the present inventionwas smaller than that of lead released from the fly ash treated withcement only even though the amount of the treating agent of thisinvention added was smaller than that of cement added. Thus, the amountof lead released from the fly ash treated with any one of the treatingagents of the present invention was smaller than the regulated value.

EXAMPLE 23

40 parts by weight of aluminium sulfate (produced by Wako Pure ChemicalsCo.), aluminium silicate (produced by Wako Pure Chemicals Co.), silicondioxide (produced by Shionogi & Co.) or aluminium phosphate were addedto 60 parts by weight of ordinary portland cement (produced by UbeCement Co.) and well mixed to obtain treating agents (23-1) to (23-4).15 g of any one of these treating agents were added to 50 g of wastewater sludge containing a large amount of copper, that had beendischarged from a plating plant, then kneaded and the resulting blendwas cured for 7 days and was thus solidified. Afterwards, thethus-formed cakes were tested to determine the effect of each treatingagent for stabilizing the heavy metals in them. To measure the amountsof the heavy metals released from each cake, used was the CAM method(California Wet Extraction Test Method) which is employed in Californiaof the United States of America. The test results are shown in Table 38below.

                                      TABLE 38                                    __________________________________________________________________________    Amounts of Heavy Metals Released (mg/liter)                                          Treating                                                                            Heavy Metals                                                            Agent Pb Cd  Hg Cr Cu Ni Zn                                            __________________________________________________________________________    Example 23-1                                                                         Treating                                                                            0.50                                                                             <0.1                                                                              0.018                                                                            0.27                                                                             29 0.40                                                                             1.4                                                  Agent 23-1                                                             Example 23-2                                                                         Treating                                                                            0.56                                                                             0.36                                                                              0.015                                                                            0.33                                                                             30 0.28                                                                             20                                                   Agent 23-2                                                             Examp1e 23-3                                                                         Treating                                                                            3.7                                                                              0.76                                                                              0.027                                                                            0.34                                                                             15 0.75                                                                             140                                                  Agent 23-3                                                             Example 23-4                                                                         Treating                                                                            3.8                                                                              0.74                                                                              0.039                                                                            0.66                                                                             64 0.82                                                                             130                                                  Agent 23-4                                                             Comparative                                                                          Cement                                                                              4.2                                                                              0.80                                                                              0.054                                                                            0.83                                                                             390                                                                              1.1                                                                              150                                           Example 23-1                                                                  Non-treated                                                                          --    8.9                                                                              10  0.081                                                                            1.3                                                                              930                                                                              1.4                                                                              3000                                          Control                                                                       __________________________________________________________________________

From the test results shown in Table 38 above, it is known that thewaste-treating agents of the present invention all have an excellenteffect of stabilizing harmful metals. Thus, it is obvious that themethod of using the waste-treating agents of the present invention issuperior to the conventional method of using cement only. As is obviousfrom these, the treating agents of the present invention are effectivefor lowering not only the amount of lead to be released from waste cakestreated therewith but also the amounts of other metals such as cadmium,mercury, chromium, copper, nickel and zinc to be released from them.

What is claimed is:
 1. A waste-treating agent for treating wastecontaining at least one harmful substance selected from the groupconsisting of lead, cadmium, mercury, chromium, copper, nickel and zinc,which contains at least one solid acid, wherein the content of saidsolid acid is at least 10% by weight,and wherein said solid acid ispowdery and is at least one member selected from the group consisting of(1) aluminum silicate or silicon dioxide each having a specific surfacearea of from 150 m² /g to less than 1.000 m² /g, wherein 50% or more ofthe Al atoms in said aluminum silicate are four-coordinate aluminumatoms, and 85% or less of the silicon atoms in said silicon dioxide aresilicon atoms having a degeneracy of 4, (2) silica gel or alumina towhich sulfuric acid, phosphoric acid or malonic acid is adhered, or acarrier of diatomaceous earth, silica gel, quartz sand or titanium oxideto which phosphoric acid is adhered under heat, (3) polyanioniccompounds, (4) cation-exchange resins, (5) ZnO, Al₂ O₃, TiO₂, CeO₂, As₂O₃, V₂ O₅, or Sb₂ O₅, and (6) CuSO₄, CdSO₄, SrSO₄, ZnSO₄, MgSO₄, BaSO₄,KHSO₄, K₂ SO₄, (NH₄)₂ SO₄, Ca(NO₃)₂.4H₂ O, Bi(NO₃)₃.5H₂ O, Zn(NO₃)₂.6H₂O, Fe(NO₃)₃.9H₂ O, CaCO₃, Zr phosphate, Ti phosphates, Al phosphates,PbCl₂, HgCl₂, CuCl₂, AlCl₃, SnCl₂, CaCl₂, AgCl₂, H₂ WO₄, AgClO₄,Mg(ClO₄)₂, ZnS or CaS.
 2. A waste-treating agent as in claim 1, whichfurther contains cement and in which the content of said solid acid isfrom 10 to 80 % by weight of the agent.
 3. A waste-treating agent as inclaim 1, which further contains cement and a caking inhibitor, whereinthe content of said caking inhibitor is from 1 to 20% by weight, andwherein said caking inhibitor is at least one member selected from thegroup consisting of silica gel, diatomaceous earth, bentonite, activatedclay, stearates, alkylamine acetates, palm oil, acid clay, activatedbauxite, activated alumina, acrylic resins, polyvinyl acetate, polyvinylbutyral, paraffin, sulfur, calcium carbonate, basic magnesium carbonate,calcium phosphate, kaolin, talc, ammonium iron citrate, and potassiumsulfate.
 4. The waste-treating agent as claimed in any one of claims 1to 3, in which said solid acid is at least one member selected from thegroup consisting of aluminium silicates and silicon dioxide.
 5. Thewaste-treating agent as claimed in claim 1, in which said powderyaluminum silicate or powdery silicon dioxide has a surface potential of-15 mV or less at a pH of 7 or higher.
 6. The waste-treating agent asclaimed in claim 1, in which the surface area of said powdery aluminumsilicate or powdery silicon dioxide contained in 1 g of thewaste-treating agent is from 50 m² /g to less than 300 m² /g.
 7. Thewaste-treating agent as claimed in claim 3, in which said cakinginhibitor is a powdery inorganic substance.
 8. The waste-treating agentas claimed in claim 3, in which said caking inhibitor is an organicsubstance coated on the surfaces of the particles of said solid acid byspraying or dipping.
 9. The waste-treating agent as claimed in claim 3,in which said caking inhibitor is at least one member selected from thegroup consisting of activated clay and calcium stearate.
 10. Thewaste-treating agent as claimed in any one of claims 1 to 3, whichfurther contains, as auxiliary component, at least one member selectedfrom the group consisting of a reducing agent, allophane and bentonite.11. The waste-treating agent as claimed in claim 10, which furthercontains at least one member selected from the group consisting ofzeolite and active charcoal.